Hello Nickii,

Welcome to the Malaysian Fish Forum.

Well what you have there is bent spine. There are a few types of bent spine i.e. deformity caused genetically, insufficient of certain nutrients in feed and also because of old age. Since you mentioned that it only appeared after the second birth, most likely the bent spine was because of old age. There's no cure for bent spines for any of the causes' mentioned. It will be only time the female will start "wasting" - stop eating, getting thinner by the day and eventually dies.

So good luck with your guppy breeding.