They're what 5 going on 6 weeks now? Round about. Yellowing of the lowers is Normal, unless it's a lot. You should typically get a couple here and there. If you've already flushed, and your pH is pretty much what you've been putting into it. I'd start with a little lighter feed. And see what happens.
What's your water source? Do you have a ppm meter?
Oh and it's your party I'm just here for the bud porn and experience lol But like I said earlier, an affordable and beneficial way of getting pH up some is the agsil 16, or the dynagro protekt. It's also potassium (k). Bunch of benefits with silica, it helps with overall plant health, strengthens cell walls, that's supposed to help ward off powdery mildew and pest.Ph down is cheap too, citric acid (lemon juice). Like I said it's your party boss. Just wanted to let you know. I try to save where I can. I've been tempted to buy pH up and down, but always been good without it. Now if I was doing hydro or something like that I might.