That's a normal temp for a chicken, but fever isn't always present in an infection. It depends on how strong the immune response is. If you have the opportunity to see a vet that is schooled in poultry, by all means take advantage.
Take a recent poop sample with you. Ask the vet to run a fecal...
I think a crop disorder has been ruled out. That leaves infection or a reproductive issue. Both of those might respond to an oral antibiotic if you have one one hand. If not, you can buy it here. https://www.kvsupply.com/item/aqua-mox-250mg-capsules-100-count/P06184/ You can try calling pet...
When they were all out free ranging, what were they eating? Is there any grass clippings, compost, leaves that they may have consumed?
Tonight, take up all food and water and then check her crop frist thing in the morning. It should be flat and empty. If it's full, that would be her problem.