FixxYurFace - I would not put your younger pair in the same tank as the breeding pair. Males will definitely fight over breeding with the females. At a minimum, the males will pester each other mercilessly when one's about to breed and the other one isn't. Even in a large heavily planted, 2 cave 75G tank. Also, the females select the male. Both males together with the females, chances are very good that the two females will breed with the alpha male and the other male will be ignored by them. While there's a slight change, depending only on the personality of the male fish, that you could keep a couple of breeding groups together in the same large tank where you can separate the caves out of view from each male, I don't see that happening in a small 29G.
Wren, while I know they can get pretty battered up and even killed when fighting, there's just no way a bristlenose with a sucker mouth could take a chunk out of another fish ..... your female definitely looks like a chunk has been bitten out of her.
Sixis - how can you be sure it's the plecos eating the shrimp and not the cories? I just don't see plecos with their sucker mouths eating shrimp. Maybe if the shrimp babies didn't get out of the way fast enough they could be sucked in to the pleco's mouth. With cories....they'd see any small moving living object as maybe live food and go for it, even their own young.