Okay, so I'm helping my friend out and we are both noobs at hydro... The bad leaf on the plant in pic #1 started out with what looked to me as a burn from spilling nutrients on the leaf, but my partner insists he wouldn't have done that. But....it has gotten much worse in the past day...and is spreading! We had some light leaks on the lid which was causing some fungus so we changed the solution out yesterday. Although root growth increased exponentially (pic #3) after the solution change, all 4 plants in this container are now starting to show these brown spots. This plant has also has a downard curled overwatered look to it all along. Pic #2 is a different strain in the same solution with no noticable problems (maybe a little lightish on the greens, but not familiar with strain (grapefruit x neville's haze) so not sure). Here is the rundown: (pic #4) Hydro Ph = 5.9 - 6.0 TDS = 300-400ppm temp = 75 degrees F solution consists of GH 3 part at 2ml/Gal of gro/micro/bloom, splash of H2O2, few drops of Superthrive, a little bit of Pyrosol (silica) runoff, and PH down to bring to desired PH atmosphere is max 85 degrees F @ 55% RH and min 74 degrees @ 47% 18/6 light cycle under 400W HPS and two 25W flourescent tubes (blue spectrum) 2'x3'x9' closet with active outtake (130CFM) cool tube on HPS, 200CFM active exhaust and 100CFM active intake with multiple passive intakes and a small rotary fan. (plenty of ventilation!) Running bubblers with plenty of air pumps 3 (60 gallon pumps with 4 5" airstones in 11 gallon and 1 60 gallon pump and one 5" airstone in 5 gallon. Growing media is a combination of things (experimental). The best plant is in a starter plug in which it was germinated with silica stone and topped off with hydroton (pic #2). The other (troubled) strain is AK-48 and I have two in starter plugs with hydroton (pic #1) and two slower plants in rockwool/hydroton (not shown). As I mentioned before I mixed the solution upin the same tub so that is the same for both units. Plants are 11 days from starting the seeds and the first 7 days were just under flouros. HPS kicked the growth up, but like I said also caused the burn where (at least I think) nutrient was splashed on. HPS is also 30" above surface level (27" above "canopy" (or lack thereof)). So any thoughts? Any help will be greatly appreciated.
Whilst I'm waiting for help, I have read through some things and decided to try lowering my ph in the "bad" bucket to 5.7 (increased availabity of P/K?) and rotating the lid so that the worst plant is no longer nearest to the HPS. Thanks in advance!
stop using superthrive, its not supossed to be used with hydro and causes buildup very quickly superthrive is whats causing your problem but mointo your ph thats causing a problem as well also did you soak your medium in ph adjusted water befor using it? and did you wash your hydroton before using it?
If the superthrive is causing my problem then why is the other plant in the same solution thriving? I thought all it had in it was hormones/minerals, and has never let me down in the past (especially when it comes to germination/sprouting), but I have never heard of it used in hydro so maybe you have something there. As for PH, what would you recomend? The hydro guy said around 6, but I didn't specify what I was growing. I think in my research I have seen some camps advocate the mid-5's and others advocate the high 5's. Being a soil guy, anything below 6 scares the hell out of me, and so I was being conservative. I did, however, soak the medium in approx. 6 ph water before using it and washed the hell out of the hydroton. Update--I changed the water in the bubbler to lower the tds to 220ppm and ph'd it to 5.7. 24 hours later, the three plants that were starting to get bad have fully recovered and the 1 bad one looks like it will recover long term as well (although the necrotic leaves are not going to heal). Thanks stitch.