yes, in most cases a curved spine is often due to genetic problems (inbreeding, weak stock, ect) and you want to ensure that you do not allow these guppies to reproduce, it will only weaken your stock further
I got so many though... it's going to be practically impossible to stop them from breeding. I guess I need to get new ones to add genetic diversity to the stock? What will happen if they get too "weak"?
Not so surprising, 2 out of 100. I'd be concerned if the deformities increase. Just cull/feeder them. When this occurs in the wild, they are snagged up by predators because they are easy targets, insuring the "million fish's " prolific strain. A ratio of 2/100 can happen even if introducing new blood. That's why they have so many durn babies.