Welcome to the forum Sonja. The platy female will take about 4 weeks to develop the next batch of fry to the point that they can survive. If they are born before that, they usually can't survive.
one of my large platys has had fry every 3 weeks - she is now seperated from any males until her sperm store is empty to let her catch up and get back to full health
when her sperm store is empty i'm going to let her have a few month break from birthing
Thanks for that. It was my guppie that was having the babies lol. They have had the black spots for ages and had nothing but have had about 20 babies now.