We have given ours chicken worming pills and they don't have any issues. My husband holds them and I open the mouth and push it in towards the back and it's gone.
Mine have more speckles and calcium spots since we culled the roosters and got a new one. One has even acted broody for almost 2 months. Stress changes a lot in chickens. A handful of treats a day won't hurt, but should be mostly grazing or on pellets. I even put cut grass in the run. Try...
Our boys and girls go in the street to get rocks. I sweep the street at times into the yard so they can eat. You can also buy bag pebbles for them. I also give more food during the day because the frost killed vegetation but give it in varying times to keep them close.
Just make sure the coop is anchored down. Our first coop like that we tied cinder blocks to the corners so it wouldn't blow over. You also might try setting it up against a structure to block the wind on st least one side.
I keep our chickens in the run until about 9 most days and free range until the roosters call them to roost. Cloudy days we see more predators in the morning so they stay up longer.
We lost about 10 gens and 2 roosters. I locked them up for about 4 weeks and the coyotes moved on. They didn't like it but it's better than being dead.
My girls only lay up high and this generation refuses to sleep in boxes as past chickens have. We put 2x4s between boxes for them to walk and perch on. They feel safer up there. Make sure your run has a roof on it or fencing.