suface activity and hermit crab lathargy problems

[Sarasobo]

today I noticed that melon dug back down In the substrate in what looks like a micro cave even tho he just got done with a fresh molt. he came up to run around for a short amount of time and then dissapeared again down in the substrate.all my crabs are under in micro caves and there is one crab that I have literally not seen since I bought him from petco about three mounths ago. Are they not happy with their conditions? I keep the temp and humidity pretty stable and a lot of them are done molting so I dont know why I hardly ever see surface activity from them :/. as a side note about this behavior this started when winter started but I dont think it has anything to do with them not liking there atmosphere my crabs went from not digging at all, to always being under not molting. Anybody have some clues as to why I hardly ever se my crabs active on the surface if their not molting or bothered by the atmosphere? dose to much humidity ever cause this? not enough natural sun? ?:?:

[CallaLily]

As long as your conditions are correct, I wouldn't worry. A lot of crabs like to dig just to dig. Also, many crabbers notice more crabs under during winter even with temp and humidity being correct.

[Sarasobo]

that makes me feel better to know, I tend to be a bit of a paranoid crab mom sometimes