There should be bigger shells available in the cage at all times. The crab may want to change shells at any time. Make sure the opening of the shell is as large as the crab's biggest claw. I've been told to feed at night and to remove uneaten food in the morning, but it looks like the food hasn't been touched. Also, I hate to leave the cage without food all day.
Hermit crabs are nocturnal, so they eat late at night and in the wee hours of the morning.
You can leave the food in all day if you like, but make sure to replace it daily. But if it's gets cooler in your house than this, then it definitely is a good idea to put a lamp near the cage. The crab seems to sleep an awful lot. It is active when I take it out, but then it wants to bury down into the gravel for a while. Yes, it's normal for crabs to sleep a lot.