I have also encountered this problem before. 1) The frog slept on the ground. 2) Gradually lost in weight. 3) no appetite. 4) Cannot climb on the glass tank(at later stage).
Things to do to save the frog:
1) Use a plastic tank to separate the frog.
2) Owing to the frog refuse to eat for a longtime. You should add some Multi-vitamin (For caged birds) and electrolyte liquid into the water to maintain his life.
3) The depth of water should be very shallow (1-1.5cm), because at later stage if he cannot climb on vertical surface, he may down into the water.
4) Assisted feed for several days. Using a plastic spoon carefully open his mouth and put a small size cricket dusted with cal + vit powder into his mouth.
5) After several days if his condition is better, keep using Multi-vitamin and electrolyte liquid, but stop assisted feed. Put some small crickets in a small container and monitor his appetite.
6) If he starts eating crickets for several days, you may put it back to the large tank.
P.S. 77 during the day and 69 at night is ok. My 20 Red-Eyed Leaf Frog are keeping 83 in summer and 62 in winter for more than 5 year. I have breed it for 3th generations, everything is fine. But make sure changed water daily and don’t use distill water!