I am not OP, by my hen looks much the same as theirs in stance and such.Yes you can crush the TUMS in some food.
But wait....you have another hen that is looking the same way? You sure they have not gotten into anything moldy, rotten or spoiled? Look at your feed, is there any mold in it?
Is the bag of feed fresh - what's the date on the bag?
How long have you had the hens?
Any changes to their environment, feed, water - anything you can think of?
Feed does not look moldy, I changed them from layer to chick starter crumbles, so it is possible that some spilled and she found a damp/moldy patch. I buy from the local mill, food looked great in the bag, date was good (a week from milling) I have since placed the feed on a board so all the spillage is caught before going into the litter.
We did have a wetter than usual spring, but it has been fairly clear and dry for a rew weeks.
We had a hot day on Thursday, which was the day I noticed her acting off. Friday I worked and didn't spend much time with her. Saturday she was still acting off (fiesty in the am, but from the late morning on she is very tired looking, not interested in kitchen scraps, almost looking like she falls asleep in the run) so I put her in a crate in the garage so I can monitor her more.
She is not eating or drinking much at all. Today I gave her a warm Epsom salt bath and tried some scrambled egg and yogurt, but she only ate a few bites. After the bath, she did seem to be contracting her abdomin, but last I checked no egg laying.
I have not done a vent check, but externally I cannot feel anything in her abdomin. I massaged her crop during the bath as well and it is fairly squishy/soft, no hard spots.