lethargy could be from stress of being handled and put into a new environment. it could also indicate health issues. when you bought the female, was she active and alert or lying around at the bottom of the cage or floor of the deli dish looking lethargic as well/
check the temperatures of your cage, if it is too hot it could be heat stress the female is suffering from, though if the male is in the same cage, he should be showing the same effects. best to double check, as some geckos may react faster to too high temperatures than others.
for now i would separate the male from the cage, since he seems to be fine, leaving her alone in the cage, so as not to stress her further by moving her into a new environment again. make sure she has water and food nearby and plenty of cover. leave alone completely for a couple days, checking only to see if she has eaten or moved around. if she starts looking skinny or shows other signs of health concerns, such as twitching, moving in odd ways etc, take her to a vet right away.
if the breeder you bought her from was using the crested gecko diet, offer her that. if the diet was babyfood and crickets, over smaller crickets than you would normally, dusted with calcium and d3, in a ceramic or glass bowl so the crickets can't get out. put the bowl where a branch overhangs it, so the gecko can get in and out easily.
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PHLdyPayne