u/Equivalent-Display27

My Thai and Deliciosa are both 2.5 years old, south east facing window, have them in a chunky non-soil aroid mix and water only when the mix is bone dry (about every 8 days or so) Have been battling mealy bugs for over a year with regular alcohol spot treatments. We went away for two weeks and came home to a large amount of mealies (understandable) and what I assume is scale and perhaps thrips? The black spots on the undersides are new also. I am confused as to their sudden demise as no new plants are in the room. Appreciate any thoughts on what this could be - I wonder if the black spots are damage from the alcohol spot treatments? TIA!