Hi Azygous, you beat me to it, Great post above!
Baby chicks are delicate creatures, as we know. If you are getting any age chicks from any outside source they are going to be stressed adjusting to their new home. More so if they have been shipped from a hatchery to your pick-up place.
Chick's G.I tract goes thru huge development the 1st few days of life. The G.I.tract isn't finished maturing when the chick hatches. The chick must adjust to both additional tract development and carbohydrate loaded feed plus environmental stress at the same time. A nutritional supplement which does not challenge the developing G.I. tract with addition uptake requirements is an excellent idea. I use Bovidr Labs Poultry Nutri-Drench. It does not need to be digested. Mainlines directly into the bloodstream. Put it in their water till the water looks like very weak tea. For the 1st 2 weeks. No other supplements needed unless a probiotic is wanted. I have been using this supplement n my collies and poultry for over a decade. Never lost a chick or had a sick chick raised on Nutri-Drench water. http://www.nutridrench.com ( 850K birds aren't wrong, smile) Just buy the smallest bottle at Tractor Supply or your feed store. ( about 6.99) It's very concentrated and that bottle should supply needs for the whole brooding season.
Here's a thread on Travel Stress in chicks:
Edited by 3riverschick - 5/15/16 at 12:43pm