How to correct Rising pH/PPM runoff

Okay so this is my first run with Hydroponics. I have been running a top feed drip line system. I am running my girls in 6 inch rockwool cubes placed in 7 x 7 pots filled with hydroton. There almost 28 days into veg from seed. I've begun to notice a couple rust spots on my girls nothing too major. I figured starting a little nute burn. So I backed off the nutes a little. I've been keeping track of the runoff and two of my girls now" the ones that are showing the rust spots and a slight droop " have a Rising pH and PPM on the runoff. I start off at about 5.6 pH about 700 PPM and the runoff ends up somewhere around 6.3 pH and 720 PPM. I was thinking that it may be a salt buildup should I flush them with 5.5 pH RO water. Or will that cause more harm than good? Any help would be greatly appreciated.

have you checked for bugs? i see lots of weird spots on some of those leaves

I forgot to mention I am using the full lineup of Botanicare nutrients. I am hand watering these girls ones daily. I noticed some issues with the girls that are now flowering also but once I got my recirculating Reservoir dialed in it went away and they are doing amazing. Also should I put them in the bigger 9 by 9 pots.

Yeah I have checked them completely and have found no sign of bugs but just in case I did spray them with neem oil.

I think those spots that you're looking at are water spots from the neem oil.