Hi Mike,
I believe kmog was referring to the strength of the nutrient solution, not the temperature. 'Too hot' is just the terminology for too strong mineral salt (nutrient) concentration. Try dropping your EC to 1.2 (or a bit less than wherever you are right now). You are aiming for equilibrium. If your PPM goes up, it tells you the plant is drinking more water than it is using nutrients from your solution. If PPM goes down, its using more nutrients than water.
This is not to say that you're res temps are not too hot - I like to keep my res at 19-21c.
All the best with your grow, let us know how you get on!