are peppermints particularly sensitive

are peppermint shrimp particularly sensitive to too much or too little of something. I am asking this as last night I lost my 4th peppermint shrimp and at the same time have not lost either of my 2 red fire shrimp, 2 porcelain shrimp and pistol shrimp.

Was wondering about lack of iodine or something (have not tested for this)

What other shrimps do you have in your tank?

Coral banded shrimps are very territorial and usually kill other shrimps. You could have a crab you don't know about. Check your fish list, might be one that is killing them too.
Shrimps in general are very sensitive to huge pH and salinity swings, they also don't like high nutrients.

how many peppermints do you have?

I had at one time a pepermint tank, swapping rock to be cleaned. Had a lot of peppermints, but kept on loosing one by one.

Eventually one night I found out why.

One pepermint swam up and molted rather fast, Pops out. Actually amazing how fast they do that. But, as soon as he molted, before he even landed back on the rock, the other peppermints attacked him. They are opportunistic, and while his shell is super soft, the others will try to eat him. Jumped up and saved him.

Same happens with hermits. As they molt, they must come out their shell for a brief moment. Then the other hermits will take that opportunity to attack, kill and eat him. Lost many hermits due to that.

They must be able to get away from the others when they want to molt.

interesting ..... I have also lost one at a time ... I had a group of 3 (who ate all my aptaisia) and then they died off one-by-one (over a period of 2 weeks). I now have another group of 3 and 1 had died yesterday .... unfortunately these do not seem to like the aptaisia so much