Hey man. How does the inside of your tub look? Is the slime foating in the res? Are your air stones covered in it?
My course of action before any chemicals or changes to the solution is to simply wash all the gunk off gently, lightproof your box, and monitor it every few hours to see if it comes back, and how fast. You might get lucky if its algae before having to act.
If it comes back, I would recommend a hydrogen peroxide dunk, and a complete flush and clean of your res. To do this, mix about a 1 part hydrox (35%) and 4 parts water into a bowl. BE CAREFUL, THIS SHIT WILL EAT YOUR SKIN!!
Then, take the baskets of your plants, and dunk the roots slowly into that solution to the base of the basket. Youll see the fizzle of the peroxide, and it'll literally eat the bad shit right off. This will devastate your root structure, however, you don't really have thick roots to begin with so I would try and clean them off, clean up your tub, solve the temperature issue and start with fresh roots. Your plants should recover.
If you don't see roots in a few days, I strongly suggest voodoo juice at that point, or just flat out starting over with lower temps (60-65) and a cleaner tub.
Also, how are you adding your hydrogen peroxide to your res? are you diluting first? what concentration are you using? how often are you adding it?