The difference we see in the fluorescent radio frequency ballasts, is that they product more of a High Pressure Mercury discharge spectrum in addition to the usual Low Pressure Mercury discharge spectrum. This is especially true for DC output ballasts such as IS (Insta-Start) ballast, as compared to the usual cheapper RS (Rapid Start) magnetic ballasts.

I'm using IS ballasts on all my fluorescents (T12, T10, T8 and T5HO ), but I also use outter Red Safety filters to eliminate stray 520nm and lower wavelengths (they don't cut out much more than the original Yellow Safety filters we hoped would work and are espectially good when combined with Red and/or Far Red phosphors to begin with).

Take care, Sal.