The flowers wilting is just their natural progression, they are finished blooming. The yellow leaf tip may be a nutrient deficiency, so a spray of water with a little soluble fert in it may be in order after recent growth during the summer. Yes, orchids even indoors do grow more in the summer because the house will be warmer, and the light is stronger from the windows.
I'd say definitely move the hepa filter so it's not blowing on the orchids. That seems to be the only change they've seen. Orchids are epiphytes that do gather nutrients from the air, so cleaning the air, and blowing dust-free air on the orchids constantly would not do them any good. They like air movement, but not a constant draft.
