I found that at the seedling stage and for the first few weeks less is more.
No nutes. Good soil. Good water. Lotsa fresh air and decent light.
If you start screwing with their environment every day, it is hard to isolate what caused the problem.
Do you log everything? Date, PH, temp, humidity, growth, amount of water given etc. This will help in the future if you clone, and will also help determine deficiencies.

I'm still new though so if anyone want's to correct me, I take well to it.