Yep, humidity is more about an average over the entire incubation period. The raised humidity for the three or four days that the other eggs will need it boosted could be offset by running a lower humidity than you usually would afterwards to get the eggs back on track to losing the proper amount of moisture.
Turning will be the real trouble. If you use an autoturner, you'd have to remove it, so then you'd have to turn by hand. And while opening the incubator briefly while in lockdown isn't an issue, opening it up long enough to turn all the eggs by hand may cause issues if it causes the membrane to dry out on any chicks that are pipped or zipping.
So you might not be able to turn the eggs during lockdown, which may or may not cause issues. Some people say that you can stop turning eggs after day 14 with no ill effects, but yours would only be on day 6 when the first batch goes into lockdown.