This just happened to me on my last hatch. All of the eggs were supposed to come within a day of each other. Silkies and pheasants. Of course the plan didn't work and the pheasant eggs came over a week late. I did a dry incubation so my biggest worry was lockdown of course. I use a still air incubator and both plugs were out. When it was time for lockdown, I positioned the pheasant eggs so that they could be turned through the plug holes rather than opening the bator. I couldn't do anything about the humidity so I just held my breath. I fashioned a coat hanger to turn and it worked pretty well. Once the chickens hatched I let the humidity just drop and then I raised it again for the pheasant lock down. All went well although the pheasant eggs did get rolled a bit by the chicks that hatched.
Good luck