I have had the same 4 equine for 2 years now. Within a week of adding Sierra to the herd everyone had the feeding routine figured out and nothing has changed in the last 2 years. So what changed a few days ago? Nothing!
In my herd Peanut gets fed first. I dump Peanut's grain in his pan and Little Bud snatches a bite then runs off to the next tub. I go to Harvey's pan and dump his grain; Little Bud snatches a bite, squeals, and then runs to the next tub. I go to Sierra's pan dump her grain, she grunts at Little Bud and refuses to let him have a bite. Then I dump Little Bud's grain. Everybody is happily munching away on their dinner. Occasionally you will see Harvey drop some grain on the ground and one of the wild rabbits will be sitting there eating beside him (Harvey loves to share his grain with the rabbits).
A few days ago something changed with the feeding routine though. Peanut decided he didn't want to eat the grain I gave him so he ran Harvey off, then Harvey ran off Sierra, Sierra ran off Little Bud and then Harvey shared with Little Bud. Nobody wanted to eat the grain that I gave to Peanut. All of the grain is the same, it came from the same bag. Eventually somebody ate Peanut's grain but I'm not sure who, probably Harvey. Ever since that evening this has become the normal routine.
I don't know if something spooked Peanut or maybe it's because of the weather change. I just really hope the horses get back to their normal routine soon. When you have 4 big horses (ok, really 3 horses plus Little Bud) running around fighting over grain it can get crazy and very dangerous. It only takes a split second for one of them (normally Peanut) to kick at another one (normally Harvey) and I could easily get caught in the middle.
Someday I hope to have a barn with stalls. Everyone will be locked in their own stall to eat. No more chaos. Little Bud won't be happy though because he won't be able to snatch a bite from everyone else's pan.