She may be gravid. My girl goes off of her food during egg session as her abdomen fills with eggs. Have you noticed her getting more restless and wanting to dig? It's important to provide your iggy with a dig box in case she does end up laying. It sounds like in the past yours may have resorbed her eggs. Mine has done this her entire life but we still offer a dig box just in case. Since she's not eating you want to make sure she has access to clean water. Egg season is the only time I've ever seen mine drink. You might want to get a vet to check her out to confirm my theory. You definitely want to get her to a vet if she's lethargic.