HCA: Hermit Crab Association

I have three generations of Isopods in my tank now. My adults have been dying and lethargic if I pick them up, which I rarely do. It is honestly disheartening. I found an original adult isopod died this morning, being swarmed with springtails. The last night I picked her up, and she was incredibly lethargic. It is kind of sad because that isopod was important to me. She was pitch black and the biggest of my Isopods. She was found with babies. I have accidentally killed three adults. I also haven’t seen any adults besides the one I talked out in like 2 months now.

Their environment should mimic your hermit crabs. They need humidity. Springtails would not kill them. What are you feeding them? Can you show me a picture of their environment?
Are you providing them with a calcium source? They love cuttlebone and course oyster shell. DO NOT PUT crushed eggshell in there. That will cut them up.
Is your water dechlorinated?

if my food bowl was an oyster shell, would it be fine?

Yes, but that isn't enough calcium for them.