In my limited experience, shipped Marans eggs are a b*tch. The membrane stretches and the chicks get too big. OK, I know the chicks get too big in shipped eggs, I guessing from research its the membranes.
Not that this helps you much, but if you REALLY want shipped Marans eggs to hatch, weigh them for the first 10 days and adjust humidity accordingly.
But, that being said, nothing is done until 3 days after the fist pip, and big eggs take more time. I don't think it was your incubator or the cooling phase, its just the nature of the process. focus on your pipped egg!
OK, thanks. I'm just surprised that coming on 22 days I have one pip.....and only half were shipped so the other 12 I had thought would be popping by now. Not even the egg from my own hen and those went on day 22, early morning. Ok, where's my wine......