The all black one may be an australorp, or could be a mix. The one with gold around the neck is a mix, likely a black sex link, and the two reds are red sex links (they come by many names, golden comets, ISA reds, cinnamon queens, etc). Nothing wrong with any of those, they are generally fairly easy birds, though I have had a few kinda testy reds. If they are getting out in the yard every day, there should be enough room. If they are inside the closed run, that's a little tight for 4 birds full time. And the inside coop depends on how the roosts are set up. Some birds like to snuggle, some demand space, not uncommon for spats and pecking when squabbling over roost space. I would do some observing to see exactly what is going on and when. If it's just a quick spat, peck and run, then it's likely just pecking order stuff, which should settle down as they mature. If it's more, then you may have a bully. For resetting pecking order it's usual to remove the bully, out of sight or hearing of the rest of the flock for a period of time. Then when they come back (theoretically) they are the newby and low in the order. Sometimes that works, sometimes not, just depends on the birds themselves.
