Over fert?

the fact they grow out of it is good, but doesn't mean it isn't caused by 'something.' Your plants look healthy. Not overly lush. This could be underfeeding as easily as overfeeding -- but again, very small balance issue, if any at all. So, don't overreact... if you try something different, give it a couple weeks to display in plant... common sense applied. 6.7pH is fine. ensure that's in range, first. ~6.8 might clear it up if it is related to N-uptake, but it could also throw other things out-of-whack. usually better to maintain a consistent, recommended pH for suubstrate and adjust nutes to that level. a few tenths of a decimal swing up and down isn't anything to be concerned about as long as it is an ebb and flow and not a trend. if you calculate PPMs from guarnateed analysis labels on your fertilizers, you can make a better guess. You are in soil, so it'll be a bit different than what i do in a soilless, but the ratios should be the same. You can see my PPMs calculated in any week of a diary.. this would be for soilless, as soil should have some in it, but will deplete over time. likely ramp up to this by end, unless you ahve a super soil context. N 120-130 P 50-60 K 180-200 These may depend on your tap water a bit. i have hard water ~250-300ppm. Ca 100-110 Mg 80-90 S - 100-110 i lkely get some Ca from tap too... using RO may need more of each of those. Again, in soil you would ramp up to this concentration, but the ratios along they way will remain the same.. you are fortifying what is in the soil, which also should be in these ratios.