HCA: Hermit Crab Association

My two crabs are drinking a lot more salt water than they usually do. The freshwater is almost always full. Are they doing this to prepare for a molt? They aren't drinking as much freshwater, so are they able to balance it out?

They know what they need way better than we do. If they are using more salt water than normal than I would guess that is what the need right now.

I know my salt water dish is used way more than my fresh, although I am guessing it is because of the straw's.

They may well be loading up on salt water in preparation to molt, or they may just want more of it right now because of a deficit of some kind. Piccolo is right that they know what they need better than we do; just keep providing clean sources of both fresh and marine-grade salt water in big enough/deep enough dishes so that they can submerge their shells (with a reliable way to climb out), and they will take what they need of each type of water, as they need it.