Seedlings going lime green - Details & photos included

[revz]

Hi all- My seedlings have had a bit of a rough go of it; I've been chasing ph around due to so off brand hydroton I think. At this point I've stabilized it to 5.5, and am looking for input. From the threads I've read this looks like either a nitrogen, sulfur or maybe cal mag def, but perhaps it is nute lock above all else?

Here are some pics:

the yellowing starts with new growth after the first set of true leaves. The green in these first leaves tends to stay there on most plants, which i believe would point away from a nitrogen def. I know that my pH has been too high, sometimes approaching 8. A big question at this point is: now that my pH is stable, is 500ppm of organic based nutes too much?

Here are some details:


Strain - Sweet and Sour Widow
# of Plants - 5
Grow Type - Hydro 40 gal rez
Grow Stage - seedling, 2 wk from germination
Setup - Ebb & Flow
Light - 250W MH + some t5's
Nutrients - Pure Blend Pro Grow, worm tea, cal mag, liquid karma, silica blast
Medium - popcorn 'hydroton'
PPM - 500, about 200 of this is PBPG, the rest is micros, lil cal mag, liquid karma, silica blast
PH - 5.5 stabilized now, has been swinging up to 7.5, sometimes 8
RH - 55% to 65%
Room Temperature -70 to 79
Solution Temperature -65 to 69
Room Square Footage - 20
Pests - None Known

I have had successful MJ grows indoor and outdoor with organic soil, and successful indoor hydro grows using PBP with peppers, but this is my first hydro MJ grow.I had a scummy / foamy rez for the first time ever, so I changed the rez once and it happened again, twice and flushed the system with h202 and cleaned everything. now it seems good and stable. Have been running it at 300ppm, but upped that this morning with the worm tea and more PBPG and it really does look like they need food. was this a bad idea? Should I run straight pH'd water for a bit? Any and all advice appreciated, -r

 

[revz]

Some background on this grow- I had to be out of town during the first few days of after germination and was not able to provide sufficient light, so they legged out quite a bit.

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Moved them to hydroton and planted pretty deep. They are generally paler then any herb I've ever seen, and look to be low in chlorophyll, but not nitrogen deficient. During the first few weeks of the grow, until the last few days, I lost control of rez pH, I believe because my rez temps have been running hotter than usual. the reason(s)?
2 variables that have changed since my previous grow are: The whole ebb and flow tray is filled with hydroton now, before I had just net pots. Also, it is a new brand, and seems very dirty despite much cleaning and also far from inert. Not only is off brand popcorn medium raising my pH (despite much cleaning), but it just occurred to me that it is also passing the lights heat into the reservoir, all the more so because there is more of it, probably about 4X the weight. I don't have a thermometer (getting one), but I know its too hot with my hand.

So, my pH hung out between 7 and 8 for days and the plant was just basically (no pun)absorbing Nitrogen and Magnesium, and seems to be nute locked. I feel terrible about this! my pH is now stabilized, and I am using ice for now to cool my rez. . Also room could use more humidity so I plan on lowering rez temp by evaporation soon, then moving on to a peltier cooler or a proper 1/10th hp chiller. I would rather not do that though. It sits on a ground floor cement slab, so there should be plenty of passive cooling potential. Before I do any of that though, I am going to remove about 75% of the hydroton, put a reflector over the hydroton net pots, and insulate the rez.

The first hydro grow I did involved a bit of beginners luck it would seem. Its a wild ride when a parameter gets out of whack.

Do you see anything else that is glaringly out of whack? Please advise--

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2 wk after germination

thanks

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