Pac Man frog shedding slim coat?

I have had two pacman frogs for about eight months then about two months ago the third one died. Since then the other two have had some issues. They seem to be sheeding their slime coat or something. The are eating some but not as well as before. When rinsed off the coat comes off. They are also housed singlely but on the same shell. They also have been kept wet enough. Any ideas?
TIA

I have had more experience with pixies than pacmans, but here are my thoughts:
It is natural for them to go through a period of aestivation. It would normally occur during the "dry" season (winter months with supplemental heat and decreased overall humidity can simulate this). During this time, the slime coating thickens and dries and helps them retain moisture until the rains come. When water contacts this shell, it softens...the frog starts moving around and sloughs the thickened slime coat. Life returns to normal. This will happen if they are a bit drier than normal and are exposed to a cleansing water (rain, rinsing, soaking, etc).
You say they are kept wet enough, but you didn't describe the setup so I cannot comment on that. Another thing that could cause sloughing of the slime coat would be an irritant. Have you changed the substrate, or cleaning process? If you use "city water" has your town adusted the treatment process (you likely won't know this, but it is done in the case of changed water quality)? Chlorine is damaging to the slime coat, and could be a factor here