Ti[ps are turing brown

I'm 5 weeks in and the tips of the leafs are turning brown. I'm using miracle grow potting soil in two and fox farm in the other 3 all are doing it. I just fertilized tonight for the second time. What might be the problem any help theyare under 400 hps.

Over feeding, and maybe too much heat.

Flush your Miracle grow.

You probably over fed them and they burnt because of it.