Hopefully when they warm up - it may stop?

Sorry ...What a pain !!!!
I have had small batches of crickets die off fast; and I take care of them all the same way. Sometimes it's just a sickly batch.
Don't put any new cricket stock with the dying ones

I purchased 1000 small crickets 3 weeks ago. ( they are in
3 big bins) the area they are in is the mid 70's.
I can count on one hand how many have died.
Common reasons for them dying:
Not enough ventilation - They need
LOTS of space, LOTS of air holes or screen top, and things to hide in. ( ie empty toilet tissue or paper towel roll)
Too low a temp...................but it sounds like you have correct that.
Soiled bins

continue to remove the dead ones as often as possible. Keep things really clean.
-I keep a separate spare/clean bin to rotate crickets from a soiled bin into the clean bin
I have to do a bin switch today...i'll take a pic and post it here later.
They will drown easily. The cotton ball/water idea is a good one!
Consider not using the flukers and change to some homemade food. There are recipes in the link I sent earlier today.
Plus .......they're not picky
Keep us posted.
Lynn