If you leave your moisture dome intact for a few days, you may find that the stagnant air and humid conditions have caused your clone to grow hairy white mold.
If touched the plant material will feel damp or mushy. This is a serious mistake, especially if it relies on growing a number of crops. To remove it, open the lid, immediately remove infected clones, and introduce fresh air into the propagator.
You should lift the lid for 30 seconds every day to encourage an exchange of fresh air. Pay attention to the correct temperature and humidity. Cutting a hole a quarter the size of the clear plastic on both ends of the lid can also help circulate air.
How big should my distributor be?
In my experience, the bigger the distributor, the better the clones. You can easily stamp the cones in the cup and cover them with plastic wrap and rubber bands if necessary.
However, using a 12-inch propagator will leave enough room to accommodate larger, more mature clones. Avoid using small multipliers 6 inches high or less as only the narrow clones will touch the wet sides and the plastic dome roof.