That is an Amazing tank!
How do you keep the rock in place?
So, is the expectation that the snails and hermits be eaten by the crabs and reason why you have to replenish so often? Doesn't that get costly?
Do you get any salt-creep on the rocks?
I've bought from them on their website about 3 years ago (if it's the same 'roesmarineworld') The frags did great and also got some extras. I would contact them asap and also take pictures if you haven't allready.