HCA: Hermit Crab Association

Hey! So, I'm a new hermit crab owner, and I've only had my two little guys for a few weeks. Since the 4th of July to be exact, since they were at the carnival I was attending.
Anyway, I've got then set up in a tank, I forget how many gallons it is, but I know it's at least 10. Above that, I think. I've done research on them, so I've been trying to take care of them the absolute best that I can. The problem lies with the bigger crab- his name is Radioactive (he's my sister's). He has a tendency to bury himself in the same spot: the back middle of the tank, and would re-bury himself if I took him out to spot clean the tank.
I've left him alone completely now for about a week or so, and he's been completely buried. But prior to that, I didn't see any typical signs of molting like I've seen described, like cloudy eyes or a chalky appearance to their exoskeleton.
He's starting to resurface a little when I last checked up on them, but I'm still worried. I mist every day, even multiple times a day when I see the humidity levels getting lower, so I don't know if it's a humidity issue or not. And the other crab (Bruce, my baby boy) has stuck close to him while he's buried. Every single time, without fail. There was maybe one night where he was more active, and even then, he was back with radioactive by morning.
Is something wrong with them? Have I been doing something wrong? I'll gladly go into more detail if I need to with how I care for them if it helps figure out if there's a problem, of if they're just weird like that. Thank you so much for reading and hopefully helping.

If you just got them last month from a carnival then they are probably just really stressed.

To help boost energy levels you can try adding a little bit of peanut butter and honey in with the rest if their food and make sure your feeding them a good mixed variety of everything they need.

Also make sure your temp is at least 75 °F and their humidity is around 80%.

What are you using for substrate and how deep is it?
What are your temp and humidity readings?

I've been using sand as my substrate, since it's affordable and a good choice based on my research.
I do keep my humidity within the appropriate range as much as possible, but I keep seeing it drop to around 60-50% about maybe an hour after i mist, which does worry me. But temp is perfectly fine, that doesn't drop or rise too dramatically and stays in range.
And yeah, I'll try giving that to them! I have seen people saying that it's a good treat or in moderation, so I'll give them some tonight ans see if things improve :]

Also sidenote now that I'm thinking of it, but I also notice that they tend to gravitate towards corners or darker spaces. That might also be a stress thing, but again, they're my first, so I'm not 100% sure. Can anyone verify if that's a thing?

With the humidity being that low it could be why they aren't moving as much.

You need to get it up as soon as possible because hermit crabs need the humidity because they have a type of gills and if the humidity isn't high enough they can suffocate.

To get it up you can put air stones in there pools (you will need aquarium tubing and an air pump) and then I would put the pools next to the heating pad and when you mist the tank mist by and on the inside where the heating pad is. You can also put a towel over the lid and that can also help.

Play sand is a good choice for substrate, be sure it is moistened so that it holds it's shape (ie- sand castle consistency). Be careful with misting too much - adding more and more water will put you at risk of flooding. The substrate should be at least 2-3 times as deep as your largest crab.
Do not dig up a crab who is underground, unless there is an emergency like a flood or bacterial bloom - resist the urge to go looking for him, he can stay underground for weeks to months at a time.
Peanut butter is a good protein and energy source, and honey is a good energy source.
What do you have as a lid to your tank? If there is nothing on it, a towel won't hold in the humidity. You need to put something that is not pourous - you can use glass or plexi glass, but can also just put plastic wrap (Saran Wrap) over the top. If your humidity drops that low within an hour of misting, then it is too low for too much of the time for crabs to survive.
What is your temperature reading? Do you have a heat source? If so, what and where is it?