Sounds like you are having humidity problems with the fattails. I use to spray 1/2 of my cages down and mix the water into the potting soil substrate and I never really had any shedding issues. They like it dark and the temperature needs to be right. A warm hide area and a cooler hide area are a must.
Hope this helps you out a little bit.
Nick
C.B. Boids
Fat Tail Gecko Cages


