Hi there ! Thanks for the helpful response and for your concern. We lost another chick yesterday. The two remaining girls are looking great, we have them on Corid, coccidiostat feed, and Sav a Chick. They are indoors, in our mudroom. They were stacking on top of each other for a few days which at first we thought was a sign they were too cold but, after doing some research, it seems that this can be a symptom of Cocci.
I am worried about these chicks, and am wondering if perhaps their condition has to do with the hatchery we got them. We were told they were 4-5 weeks old, but I have seen 4-5 week old chicks before and the chicks we have do not appear to be like them - not nearly as developed, feathered, or large. I suspect this is because they have been on a full grain and grit diet for their entire lives (not a chick starter). We are hoping for the best, but I am pessimistic. Should have known this guy at the hatchery was questionable when he said they needed to be eating oyster shells - after doing more research it appears that 1) oyster shells are not very effective as grit 2) they need to be on chick starter, not the oat groat mix he told us they have been fed and 3) an excess of calcium can be lethal at this age.
I am also concerned about Marek's. Question for you - we were referenced to Cackle Hatchery by a longtime backyard chicken owner, and are considering getting more chicks from there. If we get more chicks that are vaccinated for Marek's, should we be ok if these first chicks do in fact have Marek's? The three Rhode Island Reds have all displayed similar symptoms - lethargy, single leg paralysis, and eventually a complete loss of interest in food and water. One Easter Egger keeled over and we didn't have her long enough to see if anything was going on with her, and the other two Easter Eggers seem happy and healthy (if small and perhaps underdeveloped).