If you pen is accurate I would say the soil must be around 2.4 or lower. Bad bacteria can cause a serious drop in pH but I have heard of nothing like that. Forget the cal mag I would think as that causes yellowing but not so spotty pin holes. You could foliar them with cal mag to check. In 2/3 of the pic I would have guess ozone was causing burns. I would be checking your run off on your other girls for sure.Pull the bad one's out of the container and look at the roots. JK
I tested the soil ph it was 3.8-4.0 but i tested it with a digital water ph tester im not sure if it will be as accurate as the ones with two prongs that you use for testing soil?? either way its too low i think i need to get some dolomite lime or guano, any suggestions?