what is the pH of your run-off water? It looks like there is some pH issues and also some micro nute issues as well. Your leaf turns up is an indication of Mg def, and your older leaf being burn is an indication of N, and Zn, so when you test your run-off water for pH, make sure your last one placed in the medium has the mircro nutes as well...

if your in week 4 of flower are you adding any bloom boosters or anything??