Being a veiltail has nothing to do with deformities arising... I have bred veiltails. They may be deformed from being pet store fish, mainly. You may only walk away with a small handful of fish, if you are lucky. Get some live foods, such as BBS, microworms, etc to ensure you do get some fry from this.
I never recommend males and females together. The females may get egg bound, male may begin to tail bite, females may gang up on the male, somone might die, they may get ich, they may get infections, wounds... the problems are never ending sadly.
If you do decide to keep them together again, try finding a long tank (probably 20 gallons or bigger) and a whole lot of plants, live and fake, and hidey holes, plus filtration.
Fry: giant geno, mainly regular sized with veiltail. Is your king a plakat? You'll have shorter finned veiltails.