Emerald crabs sluggish??

[Crowxjane]

Ok, I have a 29 gallon bio cube, its cycled and been set up and running for 2.5 months or so. I have 2 emerald crabs, a skunk cleaner, assorted snails (7 or so?) and 2 small clowns. The emerald crabs have always been my favorite (I know they can have a bad rep) but mine have always been hilarious, always sneaking around, eating and I really enjoy all their weird antics. But lately they have been hiding and not very active. They have molted a few times and one is considerably bigger. Now I can only find my big one, the little one has been missing for days. This is all just so unusual as they are always out and come running when its dinner time. My parameters are normal and good, no ammonia etc. I do a weekly or bi weekly water change and try to not over feed. My large crab is also kind of covered in algae? His legs look like he has hair on them because of the amount of algae on them. Am I just over worrying about them? Am I missing something? Ugh, Im just stressing out! Thanks in advance. 

[Crowxjane]

Ok so a small update, my smaller emerald crab molted like twice?? Then I found him hanging under a rock dead?? My giant emerald crab seems fine but was picking at the dead body. Why has my one crab died after molting?? It’s kind of a bummer because they are my favorite inhabitants.