The same thing happened at my place - twice this month. The first hen was a young one and the last on, 3 1/2 weeks later, was over 3 yrs.
I couldn't find anything on them and the last one was running around, looking just fine about an hour before I found her dead in the pasture. She was still...
I've bought from Ideal in Cameron and have no complaints. (ok, just one - they didn't make good on some chicks that died right after arriving - but if you picked the chicks up that wouldn't be a situation) I think they're close to you - in 'Texas distance'.