Why? Why does it matter what the parent are? If you buy a pastel you know that at least one of the parent was a pastel or a pastel combo so I am not sure why it would be bad breeding?
To the OP if you buy a pastel you buy a pastel, you buy a pastel dam and sired are irrelevant, it would only be relevant if you were buying a Pastel carrying a recessive gene as well.
It is possible that the breeder paired several male (pastel or pastel combo) to a normal female and he is not sure which male sired the clutch.
Not knowing who neither one are indicates someone who likely re-sell animal as most breeders keep good records when it comes to their clutches.
Bottom line you buy a pastel and you pair him to a normal you will produce pastel and normal.