You think perhaps that the burning is the nutrients , but the excess wind is accelerating the burning by robbing the leaves of moisture? I've got the humidity balanced at about 50%, but i could see how consistent wind could cheat the plants of both endogenous moisture as well as ambient.

my suspicion arises from the observation that the majority of the burning is occuring on the side that the fan's blowing on. I may be barking up the wrong tree, but one must bark.