A couple things that really helped me when I was starting out:
Nutes: Look at the leaf area; the plant can only consume as many nutrients as it has the means to use. The larger the leaf, the more photosynthesis and thus more nutrients required. Seedlings need nothing for at least the first 1.5 weeks and a VERY light dose for the week thereafter. No steadfast rule here, just go with your gut.
Container: Roots hate light, they will not develop if they see light. Get an opaque (impervious to light) container and be done with it.
Temp: This is the most forgotten part of the growing equation with newbies. It MATTERS!!! The plant's metabolism is humming along perfectly (ceterus peribus) at about 70-75 deg and a little warmer for seedlings. Similar to the exponential relationship between light intensity and distance, rate of growth decreased by the square of the temperature increase. When you're sitting at 90 deg, you plant is growing less than 1/4 of its capability, not to mention the stress it's under. Cool it down and it will be happier.