When I brought home my 2 little Equadorians, they drained their salt water bowl (which was huge for them) nearly three times, even though they had "salt water" at the pet store. My assumption would be that they had that hermit crab salt water, which really isn't salt water at all.

Mine quickly molted, as well.

That salt water will help the little guy molt if he's been having to put it off due to lack of salinity.
Please do read the PPS article:PPS - preventing death
You'll want to adjust them gradually. I accidentally "drowned" a brand new crab (who was not doing well anyway) when I was new to crabbing and plopped him in a nice humid atmosphere after he had been in a very very dry pet store for at least a week. His gills couldn't take the moisture in the air.
