I've had several of the same symptoms with several of my chicks. I ordered 25 mixed heavy breed males, got 27 (from MM, btw). They all arrived mid-March (it was cold) alive. Within two days, four died (a RIR, two Buffs, and a White Rock), and within another few days, one more died (I think it was an Orpington). About two-to-three weeks later, another bird died (a Brahma), and I'm "nursing" another one (a White Rock) that had been sick, got better, and is now sick again.
The symptoms are that they all seem "drunk" or like they have a hurt leg: they just kind of waddle around and fall over, shake at times, and sit/lay down a lot.
The one I'm "nursing" has been separated from the others, and is about 1/4 the size of the others chicks (who are all about one month old now)... mind you, they were all born the same day. I'm sure he would have died had I not separated him, as I think the Brahma was killed (after he was weakened and was lying down a lot) by the other birds accidentaly stomping all over him.
So, it seems like this chick's getting better, but he just sits on his feet/legs all the time, and waddles around, or just lies on his food dish and pecks at the food. He does eat, and may drink (I haven't seen him drink in awhile, but his water level goes down, so...). But he also absolutely panics any time I pick him up (more so than chicks/chickens normally do).
I've e-mailed one of my state ag (poultry) extension agents to see if she can tell me what's wrong with this and the other chicks.
I'd hate to have to put the chick down, but I'm worried that he might infect the others if he's contagious. Plus, I raise my chickens for food, and with him being so small, I don't want to have a pet chicken and have to take care of him for a year or whatever...
MM did refind my $ for the first five chicks that died (i.e. within the 48-hour period), and their customer service was excellent; BUT, losing eight out of 27 (about 30%) of my chickens is a lot, in my opinion. I didn't have the chicks "vaccinated" (or whatever hatcheries offer to do for extra $), and do not give them medicated feed, btw.