well had 6 of these to start with lost 1 yesterday while i was at work it had started to shed before i left, came back and it was still stuck

but the 1 in the tub next to it had shed without fault so put it down to bad luck and upped their humidity. well before i went to work today another had started to shed and again when i returned it was still stuck and another had shed without fault and another is halfway through now. so 5 out of 6 have shed and looks like iv lost at least 2.
these are tiny nymphs not sure on the instar but would guess 1st/2nd so was wondering if its common to lose a few at that size? or if its something im doing wrong!!! they are all in the same type of tub with mesh at the top the same substrate (paper towel) and kept at 22c but some are fine and some arn't