I add a probiotic powder to chicks first water. Chicks raised by mother hens will get probiotics from her feces. Hen raised chicks don't get pasted vent and mine haven't had it in the last 3 years since I've been doing it.
The probiotics I add is Gro2Max.
http://www.gro2max.com/#!why-probiotics? With 5 strains of bacteria, itt is formulated specifically for chickens from research done in Egypt.
If they seem stressed, I may add some agave nectar for energy.
I don't use visible lights any more. If brooding a bunch of chicks I use ceramic heat emitters or for just a few, I use a premier heat plate. That way I can give them hemeral lighting with a dark period each night.
Red light hides wounds but blue light is more calming to chickens.