Why did my Iris's first year bloom purple petals then the following year bloomed white petals?

I can top that one. The first year my Iris didn't bloom at all. It had nice, big healthy looking leaves, but never a bloom. The next year it bloomed like crazy and it was purple petals. This last year it bloomed white background with the purple running thru it..





THEN, after the petals died, they kept coming back bigger and bigger the rest of the summer and lasted in bloom until after the first frost.....





I would think it was a plant I forgot or whatever, but it is the only Iris I have ever planted. Strange huh? No difference in fertilizer, sun, water, nothing!! Perhaps they should be renamed the ';Iris Surprise';.Why did my Iris's first year bloom purple petals then the following year bloomed white petals?
possibly you forgot where you planted something. Sometimes portions of a plant will streak due to virus, but rarely changes the entire thing