Is my hermit crab fixing to molt?

ok so my hermit crab ,Zig, sits inside his hut all day and night he never comes out. I currently have 2 hermit crabs Zig and Honey Bee. I know he is alive because I play with him and Honey Bee almost every day. Ok so the other day I noticed that the ends of his legs were turning red. When I bathe I bathe him in lukewarm water so he won't burn. So is Zig fixing to molt? if so what is the best way to care for him while he molts?