No worries Rainbow serpent, a lot of people have no idea about the painted shells, especially the pet shops, at the end of the day they dont care about the hermies health, all they want is the money!
There are a couple of other things I noticed with your hermies. Are you using an everyday desk lamp for their light? If so, this is harming them. Hermies require proper reptile globes, the normal house light globes are really bad for them, they are too drying, they zap any humidity out of the tank and they are very drying on the hermies themselves.
Here a few more tips proper & correct care:
1.Our hermies here in Oz require a temp of 26-28c and the humidity needs to be 70-80% They require humidity in order to breathe through their gills, if there is no humidity in the tank then they suffocate.
2.They require a nice soft substrate like sand, it needs to be at least twice as deep as the size of the hermie. DO NOT USE SHELL GRIT, WOOD SHAVINGS OR SAWDUST OR THAT AWFUL COLOURED SAND. you need nice natural sand. The shell grit they can not bury in and it actually scratches them, its like us trying to sleep on steel wool!
I have the sand 6 inches deep in my tank.
3.They need many shells to choose from.. at least 4-5 for each hermit. They shop for their shells like we do for clothes, they are very picky with their shells, so the more you have for them to choose from, the happier and healthier they will be.
4.DO NOT feed any of the commercial stuff they sell in pet shops. There are ingredients in these foods that harm the hermies, feed them fresh fruits, vegetables, tinned fish like tuna and sardines, chicken, bits of cooked meat, popcorn as a treat, peanut butter as a treat and honey! There are heaps and heaps of foods you can feed them.
5. They MUST have a salt water dish AND a fresh water dish available to them 24/7. DO NOT bath the hermies, put a salt water dish in there cage that is deep enough for them to submerge in if they want to. You can put some pebbles or sea sponges in the dish so the small hermies can crawl out if they fall in or if its too deep for them. Taking them out and bathing them yourself causes them alot of STRESS, if you supply them with a dish they will have a bath when they want to.
6. You must use a water conditioner in all the water you put in there cage. Any aquarium water conditioner that removes chlorine and chloramine from the water is fine.
7. DO NOT ever dig up a crab, every so often the crab buries down underneath the sand and sheds his exoskeleton. This takes anywhere from a week upto 3 months depending on the size of the hermie! If you dig them up or disturb them they will die. This is very very important!
8. Do not use Painted shells!
There is so much more information on hermit crabs, the crab street journal forum and the hermit crab association forum are excellent and will give you the best advice you can find