Our 22000 gal SWG outdoor pool has started to make everyone cough when the water feature (slide and waterfall) is running.  I have taken the water to my local store to analyze and for the most part (Chlorine was actually slightly low) everything is in balance.  The things that I have recently done:

Changed the cartridge filters (Pleatco brand), added PhosFree, added 6 lbs CYA (only read 25 in my analysis so still low).

It is only when the water feature runs or vaporizes the pool water.  I have wondered if it may be related to the construction of the feature.  Our pool is new but it has been dragging on for 3 summers now.  The pool guy has added new Epoxy on the slide to make it smooth but not sure if anything else has been added.

Everyone I have asked is baffled.  Any thoughts?