Little Pebbles' antics really intrigued me last night and I couldn't fall asleep so I did some research on various aquatic life forums, webpages, etc. Turns out, they might already be molting.
Molting or moulting is the process by which crustaceans shed their exoskeleton as their body grows. The new shell remains soft for a period before hardening. This process is also known as ecdysis.
It is important during the molting process to provide areas for burrowing or hiding that will shield them from light. The molting process can be stressful (imagine if your body was involuntarily trying to break out of your own skin), especially after shedding of the exuvium, their soft new shells make the little crabbies vulnerable to their surroundings. Their environement should be maintained at the usual temperatures, clean and undisturbed.
From now, if I see BamBam or Pebbles lying on their backs or whatever, I am not touching them at all. What I will do is change their water over the weekend to make sure they'll be alright after they've shed their skin. *sob* They grow up so fast.