I have 21 chickens all healthy looking and very active. But yesterday DH and I were working int he coop I turned up their bedding and sprinkled DE, washed and refilled waterers and refilled their feeder with Layer feed. I also sprinkled DE on the roosts and added more straw to the nest boxes. As we were standing outside of the coop watching them I noticed 2 chickens opening their mouths stretching their necks and then closing them back up. they were drinking and eating fine. they get 2 cups of scratch and 2 cups of BOSS daily in the run, with plenty of fresh water. It has been cold here lately, yesterday was probably about -5 which is I think 18 - 20 F?? the chickens are active, laying fine, no mites, clear eyes and nose, nothing in throat (i looked) I picked them both up and inspected them very well. apart form a little mud on their feet from the run. the only thing I found a bit off was their crops they seemed a bit full but I took another chicken who wasn't exhibiting that behaviour and her crop is much the same. I am pretty new at chickens so I do not exactly know how a crop is supposed to feel ??!! today they did it a few times again but they are still eating / drinking and laying just fine, they ran to me and DH they minute they saw us to get their treats....and the crops feel fine btw. I need some advice?? I have read a few posts on here about chickens opening and closing their mouths but couldn't find a post that even related to this. could the DE have caused a mild irritation maybe? or is this something else???