Does Someone Know What MAy Be Causing This?

whats your PH?
usually between 5.5-5.9, about a week ago i did see it go up to 6.6 after i added some new airstones to my res. i dunno y new airstones raise ph but they always do haha, i usually check it 1-2 times a day with a calibrated hanna ph meter
 
Im using filtered tap water, botanicare nutes pro grow at 1/2 strength from 1/3rd, adds liquid karma, and cal-mag subs, i have another plant right beside it its actually 2 days younger and about an inch taller but it looks healthier, both are auto strains, a lowrider #1, and a smurfberry, they have been transplanted in my aerochamber for about 9 days, both half doubled in hight, one is just sickly looking, my ppm of the filtered tap water usually starts of at 68
 
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