Sick baby chicken

I picked up a 6 pack of baby chicks from my local feed store last week. I noticed this morning one was acting lethargic and not eating or drinking. I separated the sick chick from the other birds and gave it some water. Within minutes, it discharged a white milky pee/poo like substance. I have given it some water a couple more times and tried feeding mashed-up feed with a little honey in it (information I found while search for tips on caring for a sick baby chick). It has dark circles under it's eyes. It does not really cheap much or act like it is in pain, only acts very disoriented and falls down and sleeps a lot. I checked it's behind and its all clear and looks normal. I have checked on the other chicks several times and none of the other new chicks are behaving this way. Their poo is normal and are eating and drinking fine (and are having fun trying to fly around the brooding box). I checked the sick chicks body and it does have one tiny little dark scab looking thing in the breast area.

Does anyone have any information on what may be happening to this sickly little chick?

Welcome to BYC. Be sure and dip it's beak into the water rather than try to force feed, since you don't want it to choke. Try some electrolytes for a day or two. You can buy them in packets to add to water, or you can make them. Here is a recipe for a quart or liter:

1/8 tsp salt substitute (leave out if you don't have it)
1/4 tsp baking soda
1/4 tsp salt
1 tsp sugar
1 Quart or Liter of water