As long as you have sufficient air circulation you should be OK, but you are the only one that can see if it is getting the air circulation it needs. There should be some air holes in the plastic dome to allow for the actual circulation, assuming enough air is coming up through the
growing medium to provide that circulation, otherwise it just becomes a air pocket. Also the air circulation should help provide cooler air under the domes. Although I would think it would be easier, and better to have one dome covering all of them, instead of one for each individual plant.
There are other elements that plants get directly from air other than co2, but but as long as you have good air circulation you should be fine there. I am not familiar with the heat and humidity needs of the plants your growing (as well as the growing conditions). But if it were me, I would not create the plastic dome over all of them. Perhaps on half of them, and keep track on how they are doing, and go from there.