Help! Discolored leaves

Ok im new to this forum and to forums in general really, I just really need some help and this looked like a great place to find it. Im a semi expericanced grower but this is the first time ive run into this problem. My ladies are between 3-5ft tall, and are 4 weeks into flowering. White Widow, and juicy Fruit. The White widow's fan leave are starting to yellow and have small brow spots coving the leaves and is spreading all over. Im growing with miriclegro potting soil and just using tap water. I have a 400 hps light 24in from my tallest plant. My grow room in in a basement closet with ventilation. Ill attach some pics to try and point out my problem , any help or suggestions would be really appreciated. thanks

have you done a ph test on the water?

the ph is about 7.4

is that reading from the spiket? test the water before adding anything so you know your source, then check again after adding whatever you typically add to your water and lastly check the run off.