So I use fox farms and I would have to respectfully disagree. I have never burned my plants. I have had to deal with nute lock once and was able to clear it up with just flushing with water and Epson salt. It is hard to tell under the burple light what is actually going on. With fox farms I usually feed about a tsp less then the recommended amount. What is your medium? Did you use perlite? Honestly 40% humidity isn't bad. Hopefully everything works out for you.