Like ILovelace said, they will eat when they are ready. Keep them hydrated and offer food once a week. However if you feel there maybe some underlying reason for the long fast, you mentioned lethargy, a trip to the vet may do the trick. Its up to you as a keeper to judge when that extra step may be needed. If it makes you feel better I have a male who hasn't eaten since July and has lost around 300g. He goes into super breeding mode every season. He eats great other wise so it drives me nuts. Needless to say he's getting the year off.
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