Help:illness

[Ldu4890]

My partners tree frog became suddenly ill. It excreted a thick white fluid from its skin. Sadly it has passed on. I need help understanding what went wrong. I attached a picture. At that point he was being moved to find treatment. Sadly no local vets treated frogs. We bought a 1 16 inch by 16 inch by 24 inch standing case. Blue bulb. Auto water sprayer on timer, water dish, climbing stone, and fake plants attached to the side. Frog was happy and healthy previous night and took a sudden turn for the worse and died an hour after he started secreting the white fluid.