Sounds like a shed coming. Pink belly, loose skin or as you say "squishy", dull eyes are all the first signs of a coming shed. This would be when you need to bump up your humidity.

Signs of an RI are mucus, stringy saliva, yawning, keeping head tilted up, labored breathing, clicks, pops, fail to feed, smear marks on cage walls and water bowl.

Posting some more info on your setup we could probably help keep your cage temps up. My home is 68 at all times and I have two glass tanks that are running great. Adding thick art paper or poster board to the back and sides(outside) can help retain some heat and if offers a feeling of security.