What am i doing wrong? why are my leopard geckos dying.?

Its simply the temp they probably dying because they are not getting enough body heat. Leopard geckos are desert reptiles and need to be in a 90-95 degree F during the day and a 70-80 degree F at night if the temp drops below zero degrees C that is way to cold! I think its the temp because everything youve been doing so far sounds right just the temp doesnt. If that doesnt help you need to take them to a vet ASAP because it could be a disease like impaction or parasitic.