> I have never had any whites in my yard.
I've looked at your pictures, since you have never grown a white iris
in your yard and iris do not revert back to a different color, your
purple will always be purple.
I think Robin gave you the best answer, probably a seed pod dropped
it's seeds and they have grown and bloomed, now you have a mixture
of seedlings blooming. I don't think it would be correct for anyone
to give you a possible name for your unknown white.
If you have sprayed roundup around you purple bed, that could
cause purple iris to be white with purple streaks and so on, usually
deformed, but I didn't see any evidence of roundup damage from your pictures.