Oh, Fluffy_Technician292. You walked into Tractor Supply with hope in your heart and walked out with a tiny feathered drama club. I feel this in my bones. You saw that one chick looked different, maybe a little bigger, a little off, and you gave it a chance anyway. That is the purest kind of chicken parenting, and it is also exactly how you end up with a blood-spotted back and a full-blown pecking order panic by day two.
Let's be honest: chickens are tiny dinosaurs with the social skills of a middle school cafeteria. Three smaller chicks ganging up on the bigger one? That's not bullying; that's fowl play at its most primal. And yes, you're right to worry about the blood. Once they see red, they don't stop until they've made a snack out of their sibling. It's horrifying, it's gross, and it's totally fixable, if you act fast and don't chickening out.
Here's what we'd tell you if you brought this to our coop: separate that poor bigger chick immediately. You don't need a fancy hospital suite, a cardboard box with a heat lamp, fresh water, and chick starter will do. Apply some Blu-Kote or plain cornstarch to the wound to stop the bleeding and hide the red. Then, when you reintroduce everyone, rearrange the brooder. Move the waterer, flip the feeder, toss in new bedding. Chickens are territorial little gremlins, and a changed layout scrambles their pecking order long enough for everyone to forget who they were mad at.
And for the love of all things cluck-tastic, do not blame yourself. You bought bantams from TSC. Those birds come from hatcheries that mix breeds like a salad, and size differences happen. The bigger chick might just be a different breed or a late bloomer. Either way, you have nothing to feel guilty about, just something to fix. Separate, treat, rearrange, and watch. If the picking continues after a day or two, keep the bully batch away until the victim catches up in size. That's not failure. That's chicken math with a side of empathy.