barring a hithiker, besides the
acclimation question, i'd blame the hermits. sounds like you have too many if you have more than 2 or 3, and they're probably starving unless you feed them specifically.
additionally, a 29 is way too small to support a sandsifter, and if the tank isn't well mature (at least 6 mos to a year old), there's not enuff food in the substrate to suport it. you should have at LEAST one square foot of open substrate for the star, but even that is too little
IMHO.
