Very good advice, Zac! I'll touch on a few things that you missed.
Is the heating element actually in the tank? If so, take it out and put it underneath the tank so that your crabs won't burn themselves on it as easily. Is your thermometer near the substrate? Are you monitoring substrate temperature? What are the warm/cool side temperature differences? Where is your humidity gauge (i.e. top of tank, bottom of tank)?
I personally recommend you try using purchased jugs of distilled water (or reverse osmosis-treated water) that have no "minerals added for taste." Not all water conditioners are safe for crabs and, ironically enough, I don't think the crab water conditioner is safe. However, I'm not positive about it. I know that API is safe for crabs, but other than that, I can't recall. You can try searching in the search box in the upper right for your particular brand of water conditioner to see if it has been discussed at all. Also, the sponge isn't really necessary except for humidity. I recommend you change one bowl of water into a bowl of salt water. Are your bowls deep enough for your crabs to submerge in? If not, they need to be. This is how your crabs will replenish their shell water to help them breathe.
You do need to use a salt water mix intended for salt water aquarium tanks. The more common brands of safe salt are Oceanic and Instant Ocean. Mix the water according to the instructions on the bag. They do need salt water - they frequent beaches in the wild to get the food and salt from the salt water.
Play sand isn't the most recommended substrate for crabs, but it will work and has worked well for some crabbers. The sand most of the more experienced crabbers use is CaribSea Aragonite sand in either the sugar or select grain size. This sand is natural and smooth - it doesn't grit against your skin no matter how hard you push on it. Playsand isn't true sand at all - it's the leftovers from crushing rocks to a sand size. Running a magnet through playsand often results in metal shavings, which we usually try to keep away from our crabs. Also, what is the other sand you have? I haven't heard of Eco sand; I've heard of EcoEarth (coconut fiber) and Hermit crab sand (not good for crabs - do a search for it on the site and you'll find plenty of discussion on it).
I'll look at your post in the nutrition section in a few minutes, but I recommend you search for "food groups" on this site. There are multiple posts with a description of what your crabs need on a daily basis. Additionally, the Epicurean Hermit site (
http://www.epicurean-hermit.com/index.php?topic=2.0) has a very extensive list of safe foods to feed your crabs. The bottom line is that they can eat most of what we do, minus the seasonings. They need a lot other than that, though, so please do look at the food groups. If you can't figure out where to find some of the odder foods (flower petals, etc.), try looking at the addiction store -
http://www.hermitcrabaddictionstore.com/. They have great crab-safe foods for very fair prices.
As for what to find for crabs, you can bring them back branches for climbing but ensure that the wood is safe for the crabs first as otherwise they can drop their shells and die in very short time spans. To check the safety, check
http://www.epicurean-hermit.com/index.php?topic=10.0 for the type of tree it is from. If you do this (or if you bring back rocks), clean them very well in salt water (the crab safe kind made from aquarium salt) and bake them at 350 (176 C) for half an hour or so to kill insects and microbes on them.
Bathing is mostly considered an unnecessary stress on our crabs now. So long as they can submerge in their water bowls, it is not needed unless you have a fight or bring new ones home. It messes up the salinity of their shell water (they monitor it very carefully and change it as needed out of the salt water and fresh water bowls) and can stress them. If they have mites, bathing in salt water will kill them and make your crabs happy, but bathing and misting (especially with new guys) would be bad. Check out
http://crabstreetjournal.com/xoops/modu ... toryid=165 for detailed instructions on how to ensure your crabs don't die from post purchase stress. This may all seem very overwhelming at first but I promise you it's all worth it! (Especially when you come home to a crab sitting on top of the tank lid looking at you like "oh, you're home now!"...yeah, it's been that kind of day.)