My platy looks abnormally fat, she has a reddish spot where her gravid spot should be, is she pregnant or is it an infection or just fat? This is a bit of a blurry photo but you can see her body quite clearly
Not to the platies if it isn't a bully. However extremely dangerous to their fry. So I would move the platies from it so they can have their babies in a tank with no fish in. Then move the platies so the fry are on their own. This gives a 100% sure chance the platy fry won't be eaten.