You may simply have a chick that is failing to thrive, but I like to try to exhaust all options as quickly as I can. You said the crop feels fine, but are you sure you know what you're looking for and where the crop is? That's not intended to be harsh in any way, but some folks mistake the location of the crop and how it should feel at different times of the day/night and/or how it operates - no offense intended in any way, ok?
The crop should be full or close to it in the evening before bed (chick's bedtime), and it should empty overnight. In the evening, the crop should feel about the size of a marble or slightly larger for a 1 month old chick. In the morning (BEFORE the chick has had any feed), it should be empty and hard to find or notice on its chest. Is this what you're finding on this chick?
You've given electrolytes, but how about vitamins? Poulty Nutri-Drench is good for a boost that often will bring a sluggish chick around and get them back on track. Poly-Vi-Sol is a human baby supplement that contains many of the vitamins that chickens need, namely the B and E vitamins and works well. Still others will use a crushed/pulverized-to-powder Vitamin B-Complex tablet to add to wet feed for a "drench" in B vitamins.
Nutri-Drench can be found at feed stores like Tractor Supply and others; Poly-Vi-Sol and Vitamin B-Complex can be found at almost any drug store.
If you're giving the crushed B-Complex tablet, dose at about 1/8 of the tablet once per day for the chick's age. Short of the vitamins and plenty of fresh Water and Starter Feed, I'm out of ideas... :-|
I hope your chick improves!
