i can offer a few but none are SUPER necessary like lowering your water temp is. However they all will help and none will hurt. I'd put in some hydrogen peroxide (3%) at 2 teaspoons a gallon every other day. An oscillating fan blowing on them would help with air flow as well. If you can get your room temps down below 80 that would make a difference.....photosynthesis slows down considerably in temps over 80 F. I can't say if this would apply to your water temp or not....just the room temp.

How often are you checkin your ph? What kind of ppm meter are you using....different ones calculate differently.