From my (very minimal!) knowledge of convict genetics - the normal color is dominant over the pink color. So if you breed a normal to a pink you would get all normal looking babies. But if you bred two of those babies, you would get 75% normal and 25% pink. Of the normal appearing babies 2/3 of them would carry the gene for pink, although they appear normal colored.
I have no idea why you got 40% pink. There must be more to the story...
I had marble convicts several years ago. When a marble convict mated with a normal, all of the fry appeared normal colored. I never did breed the fry to each other. I got rid of them before they had the chance! The last thing I wanted was more convicts. I'm not sure water is even necessary for convicts to breed...
That's great that your mama doesn't pass down her tail defect. Although I do think she's pretty cute, tail-less and all, and she's got really nice colors!
Lisa