They are on the older leaves and they keep getting...

you got it right, i mean your PH is good, and it looks like a Magnesium Deficiency, Please note: Once a magneisum deficiency is cleared up, the problem (yellowing lower leaves) will stop spreading , usually within a few days. Please note that leaves which have been damaged by a magnesium deficiency will probably not recover or turn green, so you want to pay attention to other growth for signs of recovery. i say since you done everthing right , just Wait and see how it will get in couple of days,the New growth should look normal :D i hope this helps you bro