Do bubbles kill corals?

I have some very fine bubble. So fine you have to get up to the glass to see them. Wondering if they can kill my SPS frags. I 've had two SPS frags die this week and another that has a bleaching tip.
Params are normal except my Nitrate is 15 but that's still kinda normal.
The frags have been in there for months.. can't really figure it out. One thing is my Alk swings from 7-10 over the course of a week. On my days off I slowly bring it back up to 9-10 over the course of 3-4 days then I'm not always home for a few more days it comes back down. I've been doing this for months.
Other corals and SPS seem fine.

 

I don't think that micro bubbles would kill them but I'm sure that they do harm them to some effect just as with fish.