[krackersmom2]

I noted in your run down that you do not have a humidity gauge and the temp. gauge is outside the crabitat. The placement of the gauges should be inside the tank, both themp. and humidity. The screen lid you have on the tank needs to be replaced with glass or wrapped in plastic wrap to retain humidity. Without the proper humidity, they will suffocate and die. Their modified gills require it to help them breathe. I'm sure your climate in FL is similar to mine in S. TX....since you are on the Gulf Coast. I do not use a UTH (under tank heater) and my temps. are fine with the exception when the temp. gets really cold outside. If you have an actual heater IN the sand, I would remove it. Is it like a reptile rock? Those can get too hot and burn the crabs. A UTH goes on the underside of the glass.
For Jumbo crabs your substrate needs to be at least 7 or more inches deep....depending on the size of the crab.
All crabs need a dish of fresh and salt water....made from aquarium salt. The dishes should be deep enough for your largest crab to fully submerge, but have a way for smaller crabs to get out...like a vine or piece of sponge. I would skip the bath/dip. They don't like it and don't need it. Some people give their new crabs an intital salt bath to help them "smell" familiar to the existing crabs and to check for mites. The reason for salt water is that they store it up and it helps them burst open their exo during molting.
Make some adjustments and see if it helps. I also agree that you need bigger tanks. In my 29 gallon, I have 6 crabs ranging from medium to 1 jumbo. In my 10 gallon I have 6 smalls.