when do I take out the air plugs during the hatch?

[esthermgr]

I'm hatching in a styrofoam Hovabator and my babies have started to pip. They seem to be having a hard time adn I'm worried the humidity is not high enough. Should I open up the red air plugs now or wait until after at least some of them hatch? I'm worried about shrink wrapping them from too much humidity OR suffocating them from too little air. Help!