Searched for weeks and still have a nut. / PH / ? issue - any thoughts?

I should preface this by saying that I have searched these forums, my books and other sources high and low, for more than a couple of weeks - but am still having a problem with my plants.

Here's my setup:

-5 plants in 3x3" Rockwool on a RW slab

-Drip hydro system, set to water once every 8 hours, or 3 times a day

- Pure Blend "Pro Grow" 3-1.5-4 given as directed on bottle (2 TBS/ gal)

- Liquid Karma, also given as directed (2 TSP/ gal)

- 10 gal solution in 18 gal Rubbermaid resevoir, changed weekly.

- Res PH'd to ~6.0 - most extreme readings 5.83 - 6.45

- Humidity currently at 30% (added humidifier last night) - was previously as low as 7%, generally around 10%

- Temp consistently around 71F

- 16" oscillating fan on at all times

- PPM varies between 990 (lowest) and ~1550 (highest) - generally around 1300-1450

- 8" exhaust fan only comes on if temp reaches 83F

- 4" intake fan comes on every half hour for 15min - pulls air from attic

- did not flush RW slabs prior to placing cubes on them

- clones came in 3" RW and had good root growth, but RW had algae on top when I bought them, for what that's worth.

- plants under one 400w HPS w/ Eye Hort "Super Spectrum" bulb and one 250 HPS, regular Phillips bulb - height ~10" for 400w / 7" for 250w

- System last flushed on Christmas eve with PH 6.0 water, only for about 10 min though.

I feel like I should have everything covered - and yet, 3 of my plants (White Widow) look pretty chlorotic. The other 2 (Purple Haze) are nice and green, but have very short internode length, to the point that they resemble small shrubs. All plants suffer from some degree of canoeing of the leaves. My growth on all plants has been pretty good - a couple of the WWs have grown a good 3.5" in the last 2 days.

The problem is that the leaves on my WWs appear really yellowish and the growth tips appear to be curling a bit - and as stated above, I've got canoeing on all plants.

I initially figured it might be heat stress, but its usually no hotter than 79 or so at the canopy, so I added a humidifier last night, thinking our arid climate might be the issue. When I got up this morning though, things looked about the same (humidity was still only 30% - better, but not ideal). The plants appear to me like they need more nutes, but I am afraid to go over the MFGs recommendation for fear that I've got some other ghost in the machine and that adding nutes will complicate matters.

Since this is getting long and rambling, I'll summarize my porblems as:

- yellowing of leaves
- canoeing of leaves
- slight drying at tips of leaves (the last 2mm or so)
- new growth slightly spindly looking


Can one of you ninjas here see anything in what I've described that might be causing issues? Any input will be greatly appreciated.

Brutal - I'm hoping I didn't write this up for nothing. I'd post pics , but have none with me at work.

Is there more info needed?

Maybe I should have left out all but the "leaves are yellow, dry at tips" part so that there could be the whole "what's your PH / what medium?" exchange?

I think your ph is to high, shouldn't it be in the 5.5 range for hydro?
Canoeing is caused by the plant trying to transpire through its leaves but can't. It either needs water or has a salt buildup, either way a good flushing with clean water should help.

seasmoke said:

I think your ph is to high, shouldn't it be in the 5.5 range for hydro?
Canoeing is caused by the plant trying to transpire through its leaves but can't. It either needs water or has a salt buildup, either way a good flushing with clean water should help.

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I think, based on what I've read, that my PH should be alright - although I'd certainly be interested in hearing about it if my thinking is wrong.

I may have to try flushing again more thoroughly. I wanted to do a better job the last time, but it's a bit difficult trying to tote 5 gal buckets of water to and from my attic while holiday company is around. I did have my watering schedule set at 7 times daily before I came to my senses (about a week ago), and the leaves were still canoeing so it seems that salt buildup may be my issue.

Thanks for the response.

Hey man, stop luggin buckets...leave a couple up there, fill em with a garden hose,and then store the hose. you don't need a sprayer, just an on/off switch to keep the buckets full....and I think you need to clean your system....rereading the post, you'll probably have problems, if you don't allready....most good hydro growers are going to read your 1st post and immediately know its dirty. no offence, but these guys keep their shit spotless...they do it for a reason.

seasmoke said:

Hey man, stop luggin buckets...leave a couple up there, fill em with a garden hose,and then store the hose. you don't need a sprayer, just an on/off switch to keep the buckets full....and I think you need to clean your system....rereading the post, you'll probably have problems, if you don't allready....most good hydro growers are going to read your 1st post and immediately know its dirty. no offence, but these guys keep their shit spotless...they do it for a reason.

Click to expand...

Yeah - I wasn't exactly pleased with the state of the RW the clones were in. Sure algae might be harmless, but it just seems like bad form to have it growing just because you're too lazy to do it right. I dropped my PH last night to 5.7 and am going to keep it lower for a bit to see how the plants like it. I also decreased feedings to 2x daily since RW holds so much water. Hopefully I can get some time alone to get stuff (flushing) done - inlaws don't leave for the next week.

I was tip toe-ing around my attic last night fantasizing about telling them "yeah, I have a few plants in my attic, they're completely legal under state law - now why don't you grab a couple buckets and make yourselves useful?"

I'm going to get a res and pump set up in the garage below the space so that I can pump water up. With my luck (with water) I'm afraid to run a hose up there. Does anyone have any recommendations for a pump? I need it to pump roughly 10' vertical and don't know if I'd be better with a regular hydro / fish pump or something like a sump pump.