If you get 1 or 2 they die off pretty quickly. If you get a infestation of them the under bark may be to wet. We get a few every now and again but they die off quickly.
Redfoots growth rate is something like 1 inch per year give or take. I believe by 10 years they are pretty much full size. Mojo is 10 cm and 1 year old.
I would say that is the main cause. Also do you have hard water? It could be making it appear more dry. How is the little guys poops? Color, size, consistency.
His entire enclosure should be average 84 degrees. Redfoots don't need a basking spot or a hot and cool side. Also you should be giving him a 30 min soak in warm water every day.