The Es can be hard to keep. Sometimes you end up with a hermit crab that has just had too much malnutrition before you even got it, and they just can't molt successfully. I lost the first few I had that way, and a couple others due to mistakes we all make and learn from.
Bugs definitely can sometimes be a problem, and you usually need to find the source of what is causing them to come into your tank. Did you have a covered tank? Wire lid and plexiglass or glass covering it? That's what is needed to hold in the moisture. The tank has to maintain at least 78% consistently, or the hermies gills can be damaged. For the salt water, was it ocean salt water or table salt? If table salt, that could be part of the problem.
Also, what substrate did you use? The humidity gauges need to be calibrated once in awhile to make sure they are accurate :)
I had a 20gallon tank with a sliding screen lid.When I used the wet towel,I would just cover most of the screen that way. So a full glass lid? I thought they had to have some air going through? The first time we had ants it was because I left their veggies overnight.The second time we had those white looking bugs,I thought because it was too moist,and the third was ants, IDK know why on that one.The salt was specificlly for them,"Crab Salt" in their section at Petsmart.The substrate,I statred using the tiny ,over expensive colored bags for hermit crabs as well as "Jungle " something,in the reptile section- it was all soft,no points. Then I switched sand to the vitasand in the reptile section.
Betta's: "Mint" & "Flare-Boy"
Other:6 misc catfish,Tetras,Glofish,Mollies
*RIP* To all my past little ones