You are hereWhy are my seedlings tall?

Why are my seedlings tall?

Question: Why are my hydroponic marijuana seedlings getting tall and dying?

Small marijuana seedling with magnesium deficiency - tallTall marijuana seedling in bubbleponics setup - magnesium deficiency - too wet?

Additional info:

I have two plants(seedlings) that seem to be showing signs on a Magnesium Deficiency.

I use expanded clay pellets as a medium and started them in rockwool cubes from planting as seeds. Once the seeds germinated, I placed them in a 1gallon air pot with the clay balls. The plants have only been fed with nutrients for the past 7/10days now which I used a quarter strength feed. I flushed the pots last night and have increased the feed to half strength now. Each seedling has x2 40watt CFL's directly above them and then between the plants, I have one big 300watt dual spectrum CFL. I'm using a drip system that is set up on a timer. It runs for 15mins every 6hrs. The temp is managed with a thermostat and the extractor fan kicks in when it reaches temps above 22 degrees celsius. The humidity is in the margins of 25%/35%. I maintain the ph levels at between 5.8 and 6ph. With my first plant I tried to grow, I got the same kind of leaf color as I'm getting now but the plant died within about a week which is why I'm concerned for these two plants. I have a good friend who growed hydroponic tomatoes for years, with the first plant that died, he said the rockwool was too wet but I wasn't to sure if I could take the plant out of the rockwool and plant it directly into the expanded clay pellets.

Answer: Your marijuana seedlings are growing so tall because they need more light.

When young marijuana seedlings are starving for light, they often show signs of lots of other problems.

You will improve the situation greatly by moving your CFL bulb closer to your seedlings. Small CFLs should be 2-4" away from seedlings. Large CFL bulbs like your 300W should be kept as close as possible using the "hand test." 

Place the lights as close as possible considering the heat. Place your hands where the seedlings are and with for 10 seconds. If it's too hot for you, it's too hot for your seedling. Other than that, you're trying to get your CFLs as close as you can.

Learn more about CFLs

Learn about growing with hydroponics (bubbleponics or deep water culture)

Help! My Leaves are Dying