Plants yellowing in Coco Coir

First grow using Coco, using fox farm nutrients as directed. Mars Hydro LEDs. Plants have started yellowing about three weeks into flower. Hadn't been monitoring ph due to no problems during veg. Checked water ph about a week ago and it's 8-8.2 range. So I assumed it was ph and adjusted. A week later no noticeable improvement. Should I assume it is the ph and they are recovering very slow or are there any other suggestions on what the problem is? Thanks in advance

Yep, looks like ph. Could be too much N as well.

Isn't it starange that they made it through veg with no problems using water with a ph of 8? I just think it's weird that it's only showing up now

Stutterfly said:

Isn't it starange that they made it through veg with no problems using water with a ph of 8? I just think it's weird that it's only showing up now

Click to expand...

What are you feeding them? EC for coco in week 3 should be around 1.4
If I recall, P or K precipitate more readily at a higher ph. I'll do a little research, but it sounds like you may have either locked something out or there was a reaction that made nutes unavailable.

I've been feeding them 3 tablespoons of fox farm big bloom per gallon of water since flower ever other watering using regular water.

Stutterfly said:

I've been feeding them 3 tablespoons of fox farm big bloom per gallon of water since flower ever other watering using regular water.

Click to expand...

Ack! Big bloom is a great product but it doesn't provide much NPK. Your plants are starving! Get yourself some Dyna-gro Foliage Pro and some cal-mag (I like GH Cali Magic).

Yeah N is so easily taken up at almost any PH but most other nutrients are not, so it would make sense it got through VEG and started problems in flower.
I would flush the shit out of it with PH 6 and then feed proper ratio straight after.

Isn't fox farms tiger bloom supposed to be used early flower and the big bloom late on? Or do I have it wrong way around?

Edit, I had it part right part wrong...

Use them in sequence for brilliant blooms and luscious fruit all season long. Start with Grow Big® for abundant green growth. Switch to Tiger Bloom® at the first sign of bud development.

Use Big Bloom® throughout all growing cycles to heal root systems and increase nutrient cycling. Ideal for mature, late-season flowers and fruit. For complete feeding schedules using all three formulas, go here. And to give your plants the very best they deserve, don’t forget our new Happy Frog® Potting Soil and Happy Frog® Soil Conditioner with beneficial microbes, earthworm castings, and bat guano.

coreywebster said:

Yeah N is so easily taken up at almost any PH but most other nutrients are not, so it would make sense it got through VEG and started problems in flower.
I would flush the shit out of it with PH 6 and then feed proper ratio straight after.

Click to expand...

That's good to know, thanks for the info. I don't have access to dyna grow or cal mag off hand so I guess I'll just add an extra tablespoon of fox farm with the feeding for now. Is cal mag always necessary in addition to a regular nutrient mix when using coco? I was hoping that there was one mix that does it all lol

coreywebster said:

Isn't fox farms tiger bloom supposed to be used early flower and the big bloom late on? Or do I have it wrong way around?

Edit, I had it part right part wrong...

Use them in sequence for brilliant blooms and luscious fruit all season long. Start with Grow Big® for abundant green growth. Switch to Tiger Bloom® at the first sign of bud development.

Use Big Bloom® throughout all growing cycles to heal root systems and increase nutrient cycling. Ideal for mature, late-season flowers and fruit. For complete feeding schedules using all three formulas, go And to give your plants the very best they deserve, don’t forget our new Happy Frog® Potting Soil and Happy Frog® Soil Conditioner with beneficial microbes, earthworm castings, and bat guano.

Click to expand...

I only have big bloom, I thought tiger bloom was an either or type deal, should have read up on it more I guess.

Stutterfly said:

I only have big bloom, I thought tiger bloom was an either or type deal, should have read up on it more I guess.

Click to expand...

Yep, your plants are starving.
Coco has a low CEC so you'll need some cal-mag. Any type of plant food will work, but I'd go with something high quality that's known to work well in coco. Dyna-gro foliage pro is a very good product -- and very affordable.

Stutterfly said:

That's good to know, thanks for the info. I don't have access to dyna grow or cal mag off hand so I guess I'll just add an extra tablespoon of fox farm with the feeding for now. Is cal mag always necessary in addition to a regular nutrient mix when using coco? I was hoping that there was one mix that does it all lol

Click to expand...

Coco specific nutrients have a bit more cal and mag usually, Coco latches on to calcium when its new making a lot of it unavailable to the roots. However it doesn't do it forever, I re use mine and it doesn't cause a problem anymore.
Some folks precharge the coco with calmag others just add calmag while growing. Its a common problem but its an easy work around.

And keep ph 5.8 - 6.2 for coco.
Make sure you get runoff with each feeding or you will get salt build up that eventually causes lockouts.

Flushed and increased the food. We will see what happens. Looking very yellow still

I think most people here are looking too much into it, take a step back and think. If if they were fine during vegging maybe you are not getting enough run off from your watering anymore or just not watering frequently enough . If you let your roots dry up in coco choir, The salts from the nutrients will burn them and that will show in the leaves .
There is also the possibility here that you are burning your leaves with the lights, if only the ones under the lights are affected then that would be it.
Only thing extra you need to add during flowering in coco is maybe Cal mag during first three weeks and a boost of PK , 4 weeks before harvest.

Yellowing started at the bottom and is working up. (Now the whole plants are soon to be yellowish). So I don't think it's from the lights. I allow plenty of run off during watering and don't let it get too dry so I don't think it's that either. I haven't added cal mag or PK boost just fox farm big bloom is what I've been using.

Some pics

Stutterfly said:

First grow using Coco, using fox farm nutrients as directed. Mars Hydro LEDs. Plants have started yellowing about three weeks into flower. Hadn't been monitoring ph due to no problems during veg. Checked water ph about a week ago and it's 8-8.2 range. So I assumed it was ph and adjusted. A week later no noticeable improvement. Should I assume it is the ph and they are recovering very slow or are there any other suggestions on what the problem is? Thanks in advance

Click to expand...

when growing in coco you need to boost your cal-mag if your not using a coco base nutes

Stutterfly said:

Yellowing started at the bottom and is working up. (Now the whole plants are soon to be yellowish). So I don't think it's from the lights. I allow plenty of run off during watering and don't let it get too dry so I don't think it's that either. I haven't added cal mag or PK boost just fox farm big bloom is what I've been using.

Click to expand...

I have grown in coco for a couple of years now and when they turn yellow after the stretch(first 3 weeks 12-12) usually it's because the lights are heating up thetops, not enough nutrients or root zone drying up. If it started at bottom i would say give them more N, they will get more N if you give them cal mag. Also good to note that you can increase strength of your fox farm feedings during the first three weeks of flowering. Come back down with the strength of feedings after they're done stretching.

Chunky Stool said:

Ack! Big bloom is a great product but it doesn't provide much NPK. Your plants are starving! Get yourself some Dyna-gro Foliage Pro and some cal-mag (I like GH Cali Magic).

Click to expand...

I agree. Your way underfeeding......(FF - lol)