That doesn't make it dual-sired. It makes it "Who's Your Daddy?" on the non-Pastel Pieds. There is no way to tell from this pairing who the sire is on the non-Pieds. Odds and genetics easily explain how you have both Pastel and non-Pastel Pied hatchlings in this clutch even if you only paired with the Pastel Pied male.
My thoughts exactly! It is possible that it is dual sired, but because of the pairing, there is really no way to know for sure.