Are you located anywhere near the Florida Keys or the Biscayne Bay/Miami area?
In my previous post I stated that your (and my) boat rash looked like a bacteria. Well, it seems that the state of Florida has been very actively spraying for mosquitos that carry Dengue Fever and they use two different types of broadcast spray agents: one is a standard but non-toxic insecticide to kill the adult mosquitos, and the other is a BACTERIA
to help kill off the mosquito larvae.
This aerosolized bacteria
spray could quite possibly be what is on your boat.
This sprayed on bacteria is Bacillus Thuringiensis Israelensis ... the very same bacteria that is used at ski areas to enhance the output of their 'snow guns' - and we ski patrollers and skiers have had the same damn 'bloom' on our automobiles that are routinely parked at ski areas when they they are 'making' snow. The 'blooms' happen especially on those warm (above 32°) days after a long night of 'snowmaking'.
Info: Combating Dengue Fever | Florida Keys Mosquito Control District
Comments from your boat yard reply - If they waxed, then the open 'pores' of the FRG would be filled with wax - and side surfaces of your boat not surfaced with non-skid should not be affected, the pic with the 'windows' showing wouldnt have this 'bloom' showing. If what they stated was logical, they just admitted that either that they didnt do a good job of waxing or that the wax they applied does not 'shed water'. Nice 'dodge' by your boat yard but doesnt pass the 'logic' test.
My suspicion still stands - bacteria as a strong possibility. ;-)