Small Bubbles forming in toilet bowls and tanks

[armenhamer]

Less than two weeks ago the city had someone come out to replace our water meter, they're doing this through out the neighborhood. for what it's worth we we're also having a new furnace installed while the meter was swapped out. While checking things out once the meter was changed I noticed our main floor toilet sounded different filling up after flushing. I took apart the fill valve and hooked it back up and that seemed to fix that. However, since that day and I can't be sure if I just haven't noticed it before, there's been tiny air bubbles in the tank and bowl in both the main floor toilet and the one in our basement. When you flush they go away and then reform after a few hours. The longer between flushes the more there seem to be. You can see them attached to the parts inside the tank and around the lip of the hole in the toilet bowl and around the bowl in general where the water is. Can't say that I've noticed any difference in how they flush or fill back up. All the other plumbing from what I can tell runs and drains fine as well. No noises or smells. So I'm not sure if this is normal and I just didn't notice it until now or if something is up?

I will also add you do have to bend down to get a good look at them in the toilet bowl, they are very small.

Thanks in advance for any thoughts on this.