That's a puzzler for sure. The fact that they both stopped at the same time would lead me to think it's environmental. You mentioned that husbandry was correct but you didn't mention any specifics. It looks like you have them set up in aquariums, if you have screen tops the heat might be going right out. Maybe you could cover and/or insulate the tanks? You might also try boosting or supplementing the heat at the warm end of the cage. If they are ill the heat will aid their immune systems and if it's seasonal it will bring them out of their winter rest.
I would also try to ensure that they are well hydrated. Give them a 1/2 hour bath in belly deep room temp. water for several days in a row and see if that helps.
Lack of heat and dehydration are the two most common reasons for a lack of appetite. Hope that helps, looks like you need to solve this pretty quickly!

John Yezbak
North Coast Geckos