Hermit Crabs Dont Move

So It have been 6 days since I bout my first fish (Clownfish!!!) and 2 scarlet leg hermits. The hermits are a pretty decent size but I find then just sitting in the sand. I find myself having to move them to eat the leftovers... They just sit in the sand and move their legs. Sometimes they dont even come out of their shells fully. I have 2 really really small blue leg hermits that do just fine moving all over. Do you guys have any idea what is happening???

 

Scarlets are more active at night and they are more thorough in their ways.

 

They maybe moving around at night. They also may stop doing anything in your presence until they get used to be watched.

They do molt, so you may want to add some extra shells of slightly larger sizes.

Just as a precaution I would check your parameters.

 

I woke up with one of them in the same spot. Doesnt make much sense...