Sometimes there is no rhyme nor reason to a tarantula sling dying. I lost my Tapinauchenius violaceus the other day. It was eating well, kept in a good enclosure and seemed to be thriving. However…it molted. The next day it high dived off of the cork bark onto the floor of its home and this is where I found it:
I can see nothing wrong with it, other than it is in a death curl. At first I thought it might be getting ready to molt, but it JUST DID that the day before.
In this hobby, raising tarantulas from slings is more economical from the cost standpoint, but you run a much higher risk of mortality. Beginning keepers sometimes lose slings from improper care. Even us “older-hands” will sometimes have losses that can be explained (such as my last Avicularia). The annoying thing is that there are times the little derps will kick the bucket without a good visible reason.