Whites Tree Frog - Looking very poorly

[fusss]

Hi there

I am after some help and advice please.

I had two Whites Tree Frogs, but unfortunately at the weekend one of them passed away suddenly and I’m not sure why L

They were both looking healthy and eating fine, but then the next night one of them was sprawled out on the bottom and had died.

Now my other frog is looking very poorly. He has lost vast amounts of weight and constantly sits on the bottom of the viv and never climbs and is constantly really dark colour.. He is also not eating and has his eyes closed pretty all the time.

I gave him a warm bath and he became mobile but as soon as back in the viv he goes back to the same as above.

I had them both for 1 year with no trouble, water is changed daily, fed adequately and cleaned out monthly. Temperature is just above 80 during day, about 75-78 at night.

Any ideas what might be cuasing this, and any solutions how to treat this?

Thanks!