Any platy that has shared water with a male at any point in the last 6 months is going to be gravid.
Platies reproduce using the "quantity, not quality" method. Trying to save them will lead to you being overrun with platies very quickly. Each female that you have will drop 30 or so fry every month. Those fry will reach sexual maturity with 3-4 months. Any males will then get every single female (including its mother) gravid again. The population will explode, and you will end up with more fish than water.
It is far better to let nature take its course, you will probably end up with a few fry surviving to maturity.