Dude, the plants look awesome man. Besides ur lil problem with the yellowing leaves, they look very healthy. Ur yard is very legit too, good setup.

I have the same problem with the water ph going up, but as a suggestion (which ive tried) since ur water starts at 7.2 add all ur nutes to the 7.2 water then check the ph agiain. It should drop due the acidity of nutrients and ba. I only did this on one feeding and didnt notice any problems, I dont have a ph pen yet so Im not exactly sure this will work. Could elimate the need to add ph up or down to ur feeding schedule. Idk, jus a thought as Im not a professional yet at growing but if ur willing to experiment a lil, try this on ur little plant or take some test clones.