HCA: Hermit Crab Association

Hey all! New crab momma here we brought our crabbies home on Sunday. They're still pretty shy, which is expected, but I noticed the smallest one, Pinchetta, seems to have swapped shells twice. It went from a shell that seemed too large (they head to retreat very deep into the shell to fully close it) to one that was the same shape and style that was maybe 2/3 the size. I thought it was pretty cool they found a nicer fit and were making themselves more at home. Today though i see the smaller shell is empty, as is the old shell. Not sure which new shell they chose as all 3 are burrowed under the substrate. Is it common for them to swap so frequently? I was concerned about a possible shell jacking as Sunday we did hear a chirp and the largest crab (Clawington) was very close to the Pinchetta. They weren't acting aggressive so I thought maybe Pinchetta was just in defense mode from the move.
Should I be worried? Will they bully one another if the size difference is too great? I have an extra tank and can set Pinchetta up on her own if it'll keep her safe but i don't want to isolate her if it's not necessary.
Any thoughts and feedback are appreciated, as I want to give them the best experience possible.
Thank you!

1. It's not uncommon for crabs to swap shells often. They can be picky when choosing a new one; yours could simply be testing out the different types.

2. Size differences don't really matter. I have crabs that range in all kinds of sizes and have never had an issue with any "bullying". While crab aggression is possible, for the most part you'll just witness them asserting their dominance and then moving on.

As long as you're feeding a proper diet, have offered the right variety of shells for every crab, and they aren't overcrowded, there shouldn't be any reason for anyone not to get along.
Going further, just keep an eye on them. But I'm sure you have nothing to worry about.

Thank you! I did some research on shells today and it looks like we have to get more, larger shells. For now Pinchetta and Clamp are ok, but Clawington definitely needs an upgrade. I'll be keeping a close eye on them until the new shells arrive