Hey bandit looking great so far! She's going to stretch nicely and at least double in height don't worry. As for soil ph..forget it. There is no accurate way to test your soil because it fluctuates as it dries, as different nutrients are moistened, soil density, among other things. This affects runoff as well. I spent the first half of my grow freaking that my soil ph was too low, taking samples from all over the pot to try and get a good average reading on a dry soil test kit..tried three different probes, including accurate 8. At this point I just ph my water 7 if runoff is always low and 6 if it's high. I let the buffers in the soil handle the rest. I also noticed my girls don't like rh below 50 or temps above 86. Your rh will rise as the plant gets bigger and transpires more, as well as bigger watering and evaporation. But you may want to try and cool it down a bit if possible before flower when it gets very sensitive to is environment.
I thought I'd sent you a PM about the discrepancy in soil/runoff PH, I was going to say something similar to Noob except to say it's entirely likely you have some pockets down lower in your pot that are not the same as what you see on the surface, and this is affecting your runoff PH. I've been trying to approach growing like I would a sport, do your best and leave it out on the field. In other words do what you can immediately do, and try not to think too much about the implications of the minutia.
Just remember....dry equals high. (hopefully) and that's okay. Wet and damp are when you want your ranges to be 6.2-6.7
and if the bottom of your pot's pH is WAY lower than the top, then you aren't watering to enough run-off and stuff is building up.
Yo bandit. I know your in cabinet. However, if there is anyway to pipe air from a swamp cooler in there i'd try it. Then you can turn your exhaust fan to like medium, or whatever keeps that room steady. Last year I was having the same damn problem. In a much bigger space. I run that damn portable swamp cooler 24/7 my exhaust on low and it keeps steady 79-88. I know that's a bit high. but shit I only have 15 amps to work with. Just a thought. Or...just thought this up.....freeze a couple milk jugs and put them right by your intake vent. Maybe that help.