if you think it's a crop issue then read this, the crop should feel squishy in the evening and you might even feel some grit because thats where they "chew" their food. but in the morning it should go down quite a bit with them not eating during the night.
Human Encyclopedia
... impacted crop now?hay/straw etc seems always to be involved in crop issues and for that reason I do not let it anywhere around my birds (I use shavings in the nest) ... other people say they have never had any problems but I am not willing to take that risk. If and when you do manage to get the crop empty you can add ACV (Apple Cider Vinegar) to the water (but please test the natural pH of your water first (a place that sells acquarium and pond supplies will have those cheap strips to test the water pH) and THEN add ACV till it reaches 4.5)
OR you may want to try this:
http://www.msstate.edu/dept/poultry/extsoln.htm
".....COPPER SULFATE SOLUTION
Use this solution as a treatment for mycosis (mold infection) in the crop. An alternate name for the condition is "Thrush". Use the solution as a "follow-up" treatment after flushing with epsom salt solution--refer to the section for LAXATIVE SOLUTIONS.....
Dissolve .5 lb copper sulfate and .5 cup vinegar into 1 gallon of water
for a "stock" solution.
Dispense stock solution at the rate of 1 oz per gallon
for the final drinking solution.
An alternate method of preparing the solution is:
dissolve 1 oz copper sulfate and 1 tablespoon of vinegar into 15 gallons water.
Use either solution as the sole water source during the course of the disease outbreak. Copper sulfate is often referred to as "bluestone"."
ETA: course of treatment is 3-5 days I believe)
....
BE SURE: to give them plenty of PROBIOTICS while giving them any meds. so they can keep the good bacteria levels up in their guts and avoid tummy upsets. if he isn't eating and the crop if full and mushy then he might have a problem, but if he is eating chick crumbles only then It just doesn't make sence. heres the anatomy chart again if that helps
https://www.backyardchickens.com/forum/viewtopic.php?id=10845
