How long has your ff been sitting, waiting to ferment?
2 cups of feed with however much water they will absorb (don't know if it will be 4 cups) and just a splash of ACV. 1/2 cup would be WAY too much. In fact, for 15 chicks, I think I would use a bit more feed if you want their quantity to last all day (depending, of course, on how old they are).
I started this Monday AM. I have 15 3 day old Chicks. I fed them some of the mix (I started with probably about 3-4 c of feed, 2T of UnACV, and water to cover). I have added a few 'glugs' of UnACV once since then. And I just added some more crumbles today .. I think they're going through about a cup or so a day. It's sitting in front of the fireplace right now. I have yet to see bubbling or a milky substance on top. If you have a 'recipe' I'll start it!
What happens if there is too much UnACV???