Well, step one is lower your temps in any way that you can.
Step 2 is to do the classic flush-and-feed fix... flush, with the last flsuh using 1/2 strength complete fert with micronutes, pH adjusted to suit the tested runoff pH of the water flushes.

Deficiency, toxicity, either way your temps being that high is making the problem worse.
Also, where is your fresh air coming from?