Help! Yellow leaf tips + twisting and yellowing new growth. Leaf tips curling down. (Plenty of pics)

Alright guys I need some help with this, I have a few grows under my belt now so i'm not a total noob. I know the clawing and yellow tips screams nitrogen toxicity but I am growing in Pro-Mix HP, and have added no nutrients yet (maybe my problem?). More info on the grow:

Strain: Autoflower, got a few from FastBuds, Dinafem, and Sweet Seeds. I forgot to check exactly what strains each different plant are but the problem is on most of the plants so I don't think its strain related.
Light: 400w Hortilux Metal Halide. Running an 18/6 light schedule.
Temperature/Humidity: Lights on temps are around 75-80, and lights off anywhere from 60-70. It's late fall so sometimes a cold spell can bring the temps a little lower. I think it got down to 61 or so at the lowest point last week. Humidity was lower than I would've liked for the seedling/veg stage, it was staying in the 20-40% range.
Medium: Pro-Mix HP and they are in 3 gallon Plant Warrior Pots. I'm not sure if its considered a smart pot, but they are made for plenty of aeration.
Growth Stage: They are 3 week old autoflowers, so they are vegging and some are starting to show preflowers.
Water/Nutrient Schedule: I water when the pots feel light (every 4-7 days?) and have not fed them anything yet and Pro-Mix shouldn't have much if any nutrients at all. These have received only plain waterings (tap water sat out for 24+ hours to evaporate chlorine)
pH Levels: I water with a pH of 6.0-6.2, I have read so much conflicting information on where to pH with Pro-Mix. I've read to go down into the low 5's, I've read 5.8 is a sweet spot, but the most consensus (or so I think) answers I read were 6.0-6.3. I've also read that you don't have to pH your water with Pro-Mix because the added lime in the medium balances it. My run-off pH always comes out low, water pH going in was always 6.0-6.2 in but always came out around 5.3-5.5.

I am thinking this is something pH related or they are starting to get hungry (cotyledons and the 1 fingered set of leaves are starting to yellow) because Pro-Mix doesn't have nutrients for them. Could it be a salt buildup hard tap water and/or the pH solutions? Let me know what you guys think though. I can provide more specific information as needed! Thanks!

Your ph is too low and your ppm/ec is too high. just put in ph water of like 7.0 or higher to counteract the low ph once or twice. It would not hurt to sort of flush it out so to speak. Let it have a decent amount of runoff, then don't water it for a couple days until the pot lightens up. If ph is in the low 5's, plant has a harder time taking up nitrogen.

some questions:
are you absolutely certain that there's no fert in promix? are you pHing with phosphoric acid? you know this is a fert? I don't know about your ppm being too high, but your pH is certainly too low, hence the curling of tips. I don't understand why people insist on pHing water, especially when it's just water. be careful what you read. soils are most likely designed to use water that is fresh out of the tap.

polishpollack said:

some questions:
are you absolutely certain that there's no fert in promix? are you pHing with phosphoric acid? you know this is a fert? I don't know about your ppm being too high, but your pH is certainly too low, hence the curling of tips. I don't understand why people insist on pHing water, especially when it's just water. be careful what you read. soils are most likely designed to use water that is fresh out of the tap.

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I've read that there are starter nutrients in Pro-Mix and I have read that there are none. The ingredient list was only peat moss, perlite, dolomite and some other kind of lime, a wetting agent, and the mycorrhizae. I use the General Hydroponics pH up and pH down and now that I think about it one of them is phosphoric acid I think. I've looked a little more on that and that could be my problem. Maybe the tap water itself is a little hard ppm/ec wise and combined with the pH up and down its shooting the ppm/ec up? Time to invest in a meter maybe? Pro-Mix does have a pH buffer so I probably shouldnt use any pH up or down when its got that in there. I think the tap water comes out at around 7 but when I add my fox farm flowering nutes it usually drops it to like low 5's and into the 4's. So should I just run the water through it without checking the pH? Even when fertilizing?

are you giving the ferts? you wrote earlier that you weren't using ferts yet. what fert exactly are you using, how much and how often?

Your feeding too hard. Slow down. Look at the claw. Flush and start again at half of what you were running.

blackforest said:

Your ph is too low and your ppm/ec is too high. just put in ph water of like 7.0 or higher to counteract the low ph once or twice. It would not hurt to sort of flush it out so to speak. Let it have a decent amount of runoff, then don't water it for a couple days until the pot lightens up. If ph is in the low 5's, plant has a harder time taking up nitrogen.

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Not ph. At all.

polishpollack said:

are you giving the ferts? you wrote earlier that you weren't using ferts yet. what fert exactly are you using, how much and how often?

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The only thing that has went in so far on this grow is just tap water pH'd with GH pH up and down, maybe I'm having to use too much of it and it is causing burn? I have used Fox Farm Big Bloom and Fox Farm Tiger Bloom in my previous grows. I have Grow Big just in case but autos typically don't need a high level of veg nutes because they flower in 3-4 weeks. My feeding schedule is typically water when pots feel light, nutes every other water. I would usually give them a small dose of veg nutes and a small dose of flower nutes around week 4, and then just flower nutes til week 8, then flush from there. I usually went pretty light on the feedings because they are autos, and like I said nothing but the pH adjusting has went into these yet.

Alienwidow said:

Your feeding too hard. Slow down. Look at the claw. Flush and start again at half of what you were running.

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If it is indeed nitrogen/nute toxicity it had to have come from the GH pH up and/or down, because no other nutes have went in.

DatDudeJT said:

The only thing that has went in so far on this grow is just tap water pH'd with GH pH up and down, maybe I'm having to use too much of it and it is causing burn? I have used Fox Farm Big Bloom and Fox Farm Tiger Bloom in my previous grows. I have Grow Big just in case but autos typically don't need a high level of veg nutes because they flower in 3-4 weeks. My feeding schedule is typically water when pots feel light, nutes every other water. I would usually give them a small dose of veg nutes and a small dose of flower nutes around week 4, and then just flower nutes til week 8, then flush from there. I usually went pretty light on the feedings because they are autos, and like I said nothing but the pH adjusting has went into these yet.

If it is indeed nitrogen/nute toxicity it had to have come from the GH pH up and/or down, because no other nutes have went in.

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Well theres a reason why those leaves are clawing like they are. Over feeding is my guess but it could be bugs or something else. It theyre not a new broad mite colonization or feed issues then im stumped.

Alienwidow, why do you state it's your guess to be over feeding when the grower has stated twice he isn't feeding. He's just adjusting his water to a low pH and this is the problem.

polishpollack said:

Alienwidow, why do you state it's your guess to be over feeding when the grower has stated twice he isn't feeding. He's just adjusting his water to a low pH and this is the problem.

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So how should I go about this? My water out of tap is around 6.5-7.5, it has varied a little bit. I was pH'ing it lower because "technically" pro-mix is soilless/hydroponic from what I have heard. Another question, why is my runoff coming out 5.4-5.5 when the water going in is 6.2? Maybe the pH up and down combined with the lime in the pro-mix throws it off?

DatDudeJT said:

So how should I go about this? My water out of tap is around 6.5-7.5, it has varied a little bit. I was pH'ing it lower because "technically" pro-mix is soilless/hydroponic from what I have heard. Another question, why is my runoff coming out 5.4-5.5 when the water going in is 6.2? Maybe the pH up and down combined with the lime in the pro-mix throws it off?

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It's because your promix is saturated with nutes. When those nutes dry out, they stay in the medium. When you wet them again, it disolve the left over nutes. Nutes are acidic, that is why your ph is lower coming out than going in. Measure the ppm/ec of the runoff too after flushing with regular water. I'll bet it's still pretty high.

Alienwidow said:

Not ph. At all.

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Not always true. If you ph is in the low 5's the plant can't uptake many available nutes. I just had this issue in hydro, my ph pen was reading higher than the actual ph. My ph was in the low 5's and I could not figure out why the tops were still yellowish and the plant was not drinking much water. Calibrated my pen and put the ph at 5.9, Problem solved.

For some reason people think promix doesn't have any nutes. if that were the case, they wouldn't call it promix. it has ferts in it already. there are different kinds of promix and you just pick the one you want to use. but I'm going to guess that most, if not all, of promix soil has nutes. I wouldn't worry about pH tap water, unless it's above 7.5. Then just get it to 7.0.
a potting soil grow is a potting soil grow. not technically hydro. hydro means just growing in water/nute mix only. a soil grow is a soil grow. a coco grow is a coco grow.

polishpollack said:

Alienwidow, why do you state it's your guess to be over feeding when the grower has stated twice he isn't feeding. He's just adjusting his water to a low pH and this is the problem.

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Cause i read promix and not the rest of the post. How does a plant get that big with no food in promix? Thats what i dont get. Is the cat pissin in the pot? Is he lying? Or is the issue that hes not feeding?

blackforest said:

Not always true. If you ph is in the low 5's the plant can't uptake many available nutes. I just had this issue in hydro, my ph pen was reading higher than the actual ph. My ph was in the low 5's and I could not figure out why the tops were still yellowish and the plant was not drinking much water. Calibrated my pen and put the ph at 5.9, Problem solved.
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Still not ph

Are you using tap water.

They look under fed

Alienwidow said:

Still not ph

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I missed the part where the op said they have not been fed. I saw the burnt tips and thought over-feeding w/ nute lockout. If they have not been fed, does not make a lot of sense for ph to be dropping like that (from feeding to run-off) since there are no nutes in the pro mix. Something isn't adding up.

polishpollack said:

For some reason people think promix doesn't have any nutes. if that were the case, they wouldn't call it promix. it has ferts in it already. there are different kinds of promix and you just pick the one you want to use. but I'm going to guess that most, if not all, of promix soil has nutes. I wouldn't worry about pH tap water, unless it's above 7.5. Then just get it to 7.0.
a potting soil grow is a potting soil grow. not technically hydro. hydro means just growing in water/nute mix only. a soil grow is a soil grow. a coco grow is a coco grow.

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What about when I go to start my flowering nutrient cycle in a few weeks, putting big bloom and tiger bloom into my tap water usually brings the pH down into the 5's. Should I use pH up to bring it back up to 6.5-7 or just run it through after nutes with no pH adjustment? I will double check the bag to make sure it doesn't show any nutrient content, but I am almost positive the only ingredients were peat moss,perlite, lime, a wetting agent, and microhizzae. None of these contain nitrogen that I know of, so if it is salt buildup/over fert it would have to be from too much lime in the pro-mix or im using too much pH up/down. So maybe all of the things I read about Pro-Mix needing 5.5-5.8 pH is outdated and I should pH at 6.5-7 and treat it as a potting soil?

Alienwidow said:

Cause i read promix and not the rest of the post. How does a plant get that big with no food in promix? Thats what i dont get. Is the cat pissin in the pot? Is he lying? Or is the issue that hes not feeding?

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I have no reason to lie about it as I am still really new and have a ton to learn, and I know the only way I can get the proper help to improve is to be honest. I actually thought it could have been caused by not feeding. These are autoflowers and they are at a really awkward week 3 preflower stage where they have recently left seedling stage, and are in the middle of a very short veg/preflower stage. I have noticed in my other grows that they start to get really P and K hungry right around week 4-5, so that's why I was planning on feeding flower nutes with my next water (tomorrow or monday).

MrStickyScissors said:

Are you using tap water.

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Yep, tap water. I have never tested the ppm/ec of the water here straight from tap. I should probably take that a little more serious because if it isn't caused by something that's in the pro-mix or the pH up/down solutions, then it would almost have to be hard water right? I will have to dig up some old pictures of my past grows where I ran into what seemed to be P and K deficiencies, but it could have been lockout instead of deficiency.