I've searched google and byc for the last 3 days and I can't seem to find just the right situation for what's going on with our chicks, so I figured I'd bring it up here. Background:; almost 3 weeks ago we picked up 12 chicks(3 Ameraucana, 4 Silver laced Wyandottes and 5 "Blue Splash Marans") We got them from 3 different places, Ameraucanas from a feed store, and the other 2 from 2 different private parties. All 2-3 days old and pretty close in size. We put them all in the same brooder with the same feed/probiotic protocol we've used for all of our birds. After 3-4 days, one of the Marans became weak legged and we discovered that he was missing the outside toe on both sides. We saw plenty of pictures of adults with this problem, so we separated out the Marans into a different bin since at this point there was a size disparity between them and the other 2 breeds. The Marans being smaller and no feathering at this point. He died within 24 hours of us noticing the leg weakness. Our first chick loss(we've lost a few chickens and a pullet to dogs and 2 to injuries but never chicks or illness). Sad, but I know...it happens. We moved on. We kept the Marans separated but they have access to the same feed as the other chicks. The other chicks are super active, feathering out nicely...the Marans finally start to get a little feathering but are still very small. About 1/3rd of the size of our Ameraucanas. 3 days ago about 2.5 weeks old one of the other Marans begins limping, within a few hours he mostly lays around but is very alert, eating and drinking(and this is how he remains). The following morning another begins to exhibit the same symptoms, and this morning, a 3rd. The one remaining Maran is larger and more feathered out than the other 2. There is no splaying of legs. They get up and waddle to the water/food/other side of the bin, using their wings to help them but then plop back down. The other chicks are fine, and again, same feed protocol we've always done, a chick starter with all they are supposed to need nutritional, plus probiotics in their water. We've done ACV in their water a few times as well. What could this be? Bad breeding? Deficiencies due to malabsorption? Something else entirely? Why only these chicks and not the others?