Well, there's no yellowing spots. If I turn off the HPS and look at the leaves under regular lighting there are no visible yellowing spots. It just seems to be the curling. The roots in the res seem healthy too.

As far as epsom salt, what is the purpose of that? I've heard that it ends up stunting plant growth. Also, I've been trying to keep the ph between 5.7 and 6.0. It's usually between 5.9 and 6.1. Right now, it's 6.15.