Background
I have five AK-48 plants that were sprouted about 4 weeks ago. They started under four 4' 40w fluorescent tubes. When it was evident that the plants were stretching badly (the sprouts were falling over) I added two additional 150w HPS bulbs and a small fan. This seemed to solve the problem.
I have been giving them a cup or two of water every 3-4 days. The room gets a bit warm when we have hot days, but nothing over 90 degrees or so. A fan keeps fresh air circulating from outside.
I transplanted them from their starting cups to 5 gallon buckets almost two weeks ago. The soil is all Miracle-Gro moisture control potting soil, which uses coconut husks in addition to perlite to hold moisture. Except for the stretching, they have seemed extremely healthy until now.
Problem
About 4 days ago, the edges and tips of some of the leaves began to yellow. The bottom-most leaves were the worst, with some of the leaves directly above showing symptoms as well. At this point, for better or worse, I watered the plants with some half strength 18-18-21. That was their first fertilization other than the pre-fertilized soil.
Three days later (yesterday) the plants were mostly the same (no worse), but I decided to test the PH of my tap water, which I realize I should have done when I started. It turns out the PH of my tap water is somewhere around an 8 or higher. I'm not sure exactly what it is because the bromothymol blue I have is only good for testing between 6-8ish. I tried to correct for this by using sodium bisulfate to bring the PH of some water to about 6 and watering thoroughly (about a gallon between 5 plants).
After talking to some people last night, I decided that using something made with sodium to bring down PH wasn't the greatest idea. Not only that, but the plants actually looked somewhat worse today, so I got some aquarium PH down and flushed them with lots of water (about two gallons between the 5 plants) at a 6.5 PH.
I know I've probably been fiddling with them too much, especially since they're still looking pretty healthy overall, so my plan now is to try to leave them alone until at least Monday (3 days) and see how they look. Also, I probably won't water them again until next Thursday or Friday (about a week) to give the soil a chance to dry out again.
I'm still not sure precisely what the problem is though. My first thought was Nitrogen deficiency because the yellowing started from the bottom and I hadn't fertilized at all. My next thought was N lockout when I realized how high my water PH was. Now I'm afraid the salts in the sodium bisulfate may have made things worse. One of the plants is also sagging as if from overwatering now, but I'm not surprised or extremely worried about that considering I watered them heavily two days in a row.
Whatever advice you have would be greatly appreciated!
Pictures
My grow setup
Yellowing, 4 days ago
Yellowing, today
I have five AK-48 plants that were sprouted about 4 weeks ago. They started under four 4' 40w fluorescent tubes. When it was evident that the plants were stretching badly (the sprouts were falling over) I added two additional 150w HPS bulbs and a small fan. This seemed to solve the problem.
I have been giving them a cup or two of water every 3-4 days. The room gets a bit warm when we have hot days, but nothing over 90 degrees or so. A fan keeps fresh air circulating from outside.
I transplanted them from their starting cups to 5 gallon buckets almost two weeks ago. The soil is all Miracle-Gro moisture control potting soil, which uses coconut husks in addition to perlite to hold moisture. Except for the stretching, they have seemed extremely healthy until now.
Problem
About 4 days ago, the edges and tips of some of the leaves began to yellow. The bottom-most leaves were the worst, with some of the leaves directly above showing symptoms as well. At this point, for better or worse, I watered the plants with some half strength 18-18-21. That was their first fertilization other than the pre-fertilized soil.
Three days later (yesterday) the plants were mostly the same (no worse), but I decided to test the PH of my tap water, which I realize I should have done when I started. It turns out the PH of my tap water is somewhere around an 8 or higher. I'm not sure exactly what it is because the bromothymol blue I have is only good for testing between 6-8ish. I tried to correct for this by using sodium bisulfate to bring the PH of some water to about 6 and watering thoroughly (about a gallon between 5 plants).
After talking to some people last night, I decided that using something made with sodium to bring down PH wasn't the greatest idea. Not only that, but the plants actually looked somewhat worse today, so I got some aquarium PH down and flushed them with lots of water (about two gallons between the 5 plants) at a 6.5 PH.
I know I've probably been fiddling with them too much, especially since they're still looking pretty healthy overall, so my plan now is to try to leave them alone until at least Monday (3 days) and see how they look. Also, I probably won't water them again until next Thursday or Friday (about a week) to give the soil a chance to dry out again.
I'm still not sure precisely what the problem is though. My first thought was Nitrogen deficiency because the yellowing started from the bottom and I hadn't fertilized at all. My next thought was N lockout when I realized how high my water PH was. Now I'm afraid the salts in the sodium bisulfate may have made things worse. One of the plants is also sagging as if from overwatering now, but I'm not surprised or extremely worried about that considering I watered them heavily two days in a row.
Whatever advice you have would be greatly appreciated!
Pictures
My grow setup
Yellowing, 4 days ago
Yellowing, today
