I saw the same exact thing happen to Tropical Island when they started a new bare bottom 160+ gallon SPS tank. White bacterial bloom...full bare bottom.
Also had this happen to me when starting NoPox. How are the fish? Mine were breathing harder due to O2 being consumed by bacteria. UV def...
Berghia are king. It takes a little time but it'll nuke the Aiptasia. They truly work. Can't mix them with wrasse though. Don't forget about copper bands. They can help also.