Mealies, dust, or other?
 

I've just recently noticed this greyish film on one of the leaves of my phals. Is this mealy bugs?http://img.tapatalk.com/d/14/01/10/gu8u8uzu.jpg

Nope...not mealies. Looks like it might be some old film from a past insect spray. Or, yea, it might just be dust.

Take a damp paper towel w/a little mild soap and wipe it down...should clean it right up. If the film remains you can use a little milk or water diluted lemon juice to wipe the leaves down.