And how can a shul have a mincha and maariv minyan running simultaneously?
No problem you can when necessary rely on R Yehuda that Maariv can be davened after Plag which is .12499 0f the day for instance today in Zip 11204 is 6:56:10 Gra & Rav 7:53:10 Magen Avraham.
What is problematic is the same person doing both Mincha & Maariv after Plag.