You might want to explain your brooder set up as well. This may help identify where a problem resides.
Shipping is hard on them. Did you dip their beaks for a drink when you "unpacked" them? Are they bantams or standard? I usually grind the feed for bantams to give them a good start. Hard boiled egg yolk is good to give them a boost of protein.
I ordered from Mcmurray. Yesterday afternoon I called them, at that time only two were gone, so they refunded me for two. Then last night the third died and now I'm out of the 48 hr window for them to do anything.
I have a watermelon box with pine shavings, a 250 watt red heat lamp, temperature between 90-95, 2, 1-quart waterers, and 1- 24" feeder. I'm feeding them Purina Mills medicated starter. I dipped their beaks in the water when unpacking. They all seemed to be fine except for the DOA.
Keep a close eye on them and add vitamins and electrolytes to their water. I had trouble about 2 years ago when i ordered from mcmurrays... Out of 52 chicks they sent 27 died over the course of 2 weeks. We kept mcmurrays posted over that 2 week period and they refunded us for half the order. They packed them in a box the size of a shoe box with a divider in it so it was wayyy too cramped and a few were DOA. The others that died got pnemonia from shipping. I remember reading something on here about mcmurrays having issues with sick birds which i believe wasn't tooo long ago it may be possible that they haven't fully corrected the problem.