Moldy feed could be the issue, but I think you would have seen the symptoms earlier unless you can you nail down exactly when she might have gotten into that? If it was in the last day or two, that could be your issue, and you may want to consider an Epsom Salt or Charcoal flush for your girl.
Have you given her a good external examination? We're looking for lice, mites, or any other external parasite that might be affecting her. Look closely at her vent area, under her wings where they meet her body, on her legs and feet, around her neck and just below her head. Look for ANYTHING that is moving on her and report back what you find. Photos if you find something are GOLDEN.
At 23 weeks, she shouldn't need to be de-wormed, and you didn't mention any de-worming, but intestinal parasites can be at play in lethargic birds that are still eating/drinking and whose crops are emptying as they should. A fecal float or evidence of worms in the stool are the only really accurate ways to be certain, so look closely at her stool(s), and report back what you find.
Her eyes look a bit droopy in the photo above, and you've checked her crop, so let's be sure about egg-binding, though that would be uncharacteristic of such a young bird. The easiest way to do that is lubricate a gloved finger (preferably your smallest finger), and gently insert it 1 to 2" into her vent in a slightly upward orientation if she is standing normally. You will feel the egg if it's there.
Another method is to feel her abdomen just below and in front of the vent, pushing gently upward and forward. If there is an egg in the oviduct, you should feel it. Refer to the photo below so you know you're going upward into the oviduct and not down into the large intestine.
At the end of the day, vets are our best resource for tending to sick birds, but we can rule out some things with careful examination and knowing what to look for. If you see blood in the stool, for example, you might be dealing Coccidiosis; if you see worms in the stool or on the ground, you're dealing with intestinal parasites, mites/lice, then external parasites, a thick hard(ish) mass in the crop, likely Impacted Crop, and so on.