I'll check on senior feed as well. I think I should have started upping the feed as soon as the grass got sketchy to prevent the weight loss in the first place.
Neither one had eaten much hay when I checked on them at lunch, they were both out in the pasture. What Jaydee said about the stalls is probably right, and maybe they just would be more comfortable eating outside.
My stalls have solid walls, no dividers. There's trees for shelter in the adjoining pasture, so the quick fix will be to just shut them out of the stalls when that fence is completed in a few weeks, then bring them in to feed and when the weather is bad.