You are fine to mix them at this point. The only issue might be if you have an autoturner, it makes it hard to take some out of the turner for lockdown while letting the others still get turned. Depends on the type of incubator. Sometimes you can remove some of the rails for the hatching ones. Or, you can just let then hatch on the turner. That's not optimal and it's possible some could get hurt in the mechanism if they do hatch.
If you but a second incubator, it doesn't need a turner, use it as a hatcher and put the eggs in there for the last 3 days only.
Or, wait a day, then pull out the turner and put all the eggs in without the turner. The new eggs don't need turning the first 3 days. Just mark which ones are which, remember the chicks may move them around.
