The problem is the temps. Low 80s is where the eggs should be, not upper 80s. If the perlite is too damp, they may also drown. I had this problem with my pythons. My milk snake eggs dimpled a little though, so I don't think it was moist enough, but they can always be moisted more. Can't be saved after drowning though.
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"I'll be back at 6 if not 7. 8 the very latest but definatly no later than 9...ish...Moscow time."