Not having enough information to zero in on a cause of this chick's downturn, I'm left to fall back on one of the most common reasons for a chick of this age to fail - crop or gizzard blockage. This is almost always caused by inappropriate foods and inappropriate grit for digestion.
If we are unable to glean any further information on this chick, I suggest you go ahead and start treating for digestive tract blockage. Depending on the extent of the chick's distress, I would begin by giving it a teaspoon of coconut oil, and we might need to do more later.
The best way to do this is to measure the oil out, divided into chick-size lumps, chill until firm in the refrigerator, then pop the pieces into the chick's beak. The hard part is prying open the beak, but the chick won't have any problem swallowing the oil lumps.
I happen to be treating my own chick, although it's much older than yours, for this issue, and I've had to deal with severe gizzard blockage plus sour crop. I really didn't think this little gal was going to survive, it was that bad, but after intense treatment with everything I had in my bag of tricks, it appears she's improving.
So, let's get started on your chick with the oil, and then we'll see how she does and where we'll need to go from there.
