Horses not coming up at feed time

We don't have a huge lot currently fenced in but here lately I'll call out and get the grain ready and they'll take forever to finally come up and then when Sugar finishes or gets close to finished she'll seem to spook or trot down the hill and Grace takes off after her. I can't leave the feed unattended because Rags won't leave it alone, he'll knock the buckets down and eat it all and he doesn't need any grain at all let alone the other's leftover. So what should I do differently? I have to keep Grace and Sugar separated at feed time by at least a good bit of space because Grace is head mare and runs Sugar off, the pony Rags we have a stall for and I bribe him in for treats and a small handful of grain while the big girls eat. He will non-stop persist on stealing theirs if I don't do that.

We recently added a top hot wire to the fence line on one side (barn's in the middle so I haven't run the other side yet). I did this to get them off the fence for one, they're mangling my cattle panels, and also to get them use to the idea of a hot wire fence, so when we fence in the next 2+ acres they'll be respectful of the fence and already know to stay off it. In other words, we're breaking them to the hot fence now with just one strand so when they get the rest of the land they'll already be prepared. I'm pretty sure neither of our mares have been on hot before but I really don't know. I know the first day it was on they were nervous and I don't know if that's why they're acting so spooky now too, still nervous.

Any suggestions? I don't really want to have to relocate the feeding area because I have the pony stall right now to use and won't have that if I move them.

I'm guessing you don't have stalls? Do you have a small area that you can close and keep them in until they're done? Put the pony in the stall, close the two horses into the small enclosure. Consider using feeding bags. Try also feeding them their grain and some hay, so they are less tempted to immediately run off.