Advice help?

​So I graduated college this last spring (fuck), and have started to go on dates with this one girl who is gf material. But I have still seen the two girls I used to hook up with school and text with them a bunch too.

My question is, if I start dating this one girl from the real world, do I owe it to the others to tell them that I’m about to start something with this other girl or do I just wing it because I will only see them if/when I visit school? Thanks bros.