There are a couple of ways air can get into the returns, but none of those chemicals would have anything to do with it.
There is sometimes air in the filter, which can take several days to come out if the filter started full of air.
If you have a SWG, it will create many tiny bubbles when it is active.
You might have a suction side air leak. One common place to look is the pump strainer basket lid, which might not be on correctly.