A move, new surrounding, new flock members - all these things are stressful for all of them. Provide some vitamins/electrolytes for a couple of days in 1 of your water stations (fresh water in the other).
I would get some more Corid to have on hand. Being on new ground, it's possible your oldies could encounter strain(s) of Coccidia they haven't been exposed to AND possible that the newbies haven't been exposed to the strain(s) your oldies brought with them - if that makes sense. So...I would treat all after they have been together 7-10 days. Give a course of Corid for 5 days, then after treatment provide another day or two of vitamins/electrolytes.