Yellow leaves!! HELP

[howezer]

We are using Super soil with worm castings and pearlite. Babies started out fine and now we are developing yellow leaves. We added small amounts of dolomite lime to bring up the soil pH (it was at 6.0 before the add). Water pH is 7.0. Using Miracle Grow Tomato feed (18-18-21) every other water.
400w MH, lights at 19/5, 4x4 room, 7 plants 6-8 weeks old. Temps ar 70-85 during day. Dropping to 60-65 at night. Humidity 40-45.

Whats going on!? Any ideas?

howezer Reviewed by howezer on 05-10-2008. Yellow leaves!! HELP We are using Super soil with worm castings and pearlite. Babies started out fine and now we are developing yellow leaves. We added small amounts of dolomite lime to bring up the soil pH (it was at 6.0 before the add). Water pH is 7.0. Using Miracle Grow Tomato feed (18-18-21) every other water. 400w MH, lights at 19/5, 4x4 room, 7 plants 6-8 weeks old. Temps ar 70-85 during day. Dropping to 60-65 at night. Humidity 40-45. Whats going on!? Any ideas? Rating: 5

[Rusty Trichome]

Looks like nute lock-out and overwatering. MG for tomatoes isn't the best for cannabis. Is it at least a liquid fert?

[stinkyattic]

If you do adjustments to your soil pH, you need to first determine the runoff value which is the combination of (what you put in) + (what the soil is doing to it) = (what comes out the other end). So if your water in is 7, look for the runoff pH to be about 6.7-6.9.
How are you determining soil pH? There is a sticky at the top of this section on how to do it correctly. Metal probe type 'soil pH meters' sold at garden stores are often WILDLY inaccurate, and at the very least, quite imprecise.