The easiest way to tell is to spray the UV killer on the suspect spots and check them again.Atsko sells a UV Killer kit that contains a small UV light in the proper wavelength for checking UV reflectivity, standard "headshop" blacklights project only lower wavelength UV light, but can determinethe base level of UV glow that you're probably seeing. White will look bright under a blacklight even after treatment because of it's native reflectivity, but a predominantly white camo set I recently treated was noticably duller after treatment. You can see the glow diminish as the product is applied, even on flourescent garments.