You might try getting some StressCoat+, I got mine from petco (great chemicals, great decor and food prices, not so good fish) it acts as a dechlorinater in regular doses, but when you double the dose it adds a slime coat to the fish and repairs scale damage (which will calm your deformed guppy and hopefully induce some recovery) and, just so you know, the bottle does say to dose double for fun repair, I'm not making it up
one of the main ingredients is aloe. It's a great switch for dechlorinater too! Because, it still has a good effect on the fish in small doses, just not really fin repair. And, you know, in my opinion (and seriously just an opinion) I feel better using the stress coat because now that I look at plain dechlorinater it looks almost harsh compared to stress coat, and I will never, ever, switch back to plain dechlorinater.
So, yeah, that big paragraph was just something I thought might help with your guppies recovery (I love guppies, they're my favorite) I hope yours gets better soon!
And, also +1 on the genes. I wouldn't breed the offspring though, they might carry the gene and just not show it (if it's recessive) and it might cause internal problems that show up even before birth, but aren't noticeable on the outside. But, don't cull the whole batch, just sell them with strict instructions not to breed them, or keep them in their own tank/tank divider area. Or if you're really done with all the gene talk, just feed them to the other fish (and no, genes cannot be transferred through being eaten by another. The other fish will just get a high protein snack)
Hope I helped