Well, I figured I'd make one more post with our final decision on this. Too many times I've read threads on here and there is never any conclusion, so it is hard to learn from other people's situations. So, here is our conclusion.
It has been decided that Mini will be put down. The brooder will be completely sterilized for the chicks due to hatch this weekend, and also a brand new separate brooder will be set up for our incoming chicks that will be here tomorrow. We are not going to bother with a course of antibiotic for this "could be" whatever this chick has. It's very likely his head flicking is neurological, from the medicated feed, or vitamin deficiency. However, there's the real possibility that it is something respiratory, and though it may sound callus to some... we just don't want to take that risk with our flock.
The thing that bothers me about this, is that we have a healthy flock, as far as I know. This head flicking possible sneezing has manifested in the chicks that we hatched from our silkie breeding pair. We acquired this breeding pair about 8 months ago, and they have well passed the quarantine time. However, it makes me want to take a really close look the roo and hen in the breeding pen since I know this can be passed down in the eggs. This is the first set we have hatched from this pair, and our first bantams. I have another set due to hatch this Saturday and they will be quarantined right from the start as well (just as this first set was). Luckily the breeding pair has never been integrated into our main laying flock. They have always been separate in a breeding pen. Though I know respiratory issues can be passed to the laying flock from us as we maintain both pens. Lets pray that isn't the case (and that is if the roo & hen are even carriers of some respiratory issue, even if it isn't showing in them, we don't know). I'm going to keep my fingers crossed that this is just a neurological effect. That being the case, putting Mini down would likely still be the best thing for him. I may be able to learn more after the new chicks hatch.
Anyways, I wanted to give one last update. I hope I haven't upset anybody with our decision to put Mini down. We have given this a lot of thought, it was not a rash decision. We just don't want to take any respiratory risks with our flock.
Thanks, Maah.