In my garden, if the ph get's too high, I get the "canoeing" of the leaves. (not to be confused with "the Claw, which is a low ph issue) Your new growth looks awfully yellow compared to the neighboring plant.

You mention using phUp and phDown. You shouldn't need nor use both, and if you do the ph will bounce to extremes. Keep ingoing ph steady and trust the buffering of FFOF. At least for the first couple of months in the stuff. Once the buffering depletes, you'll notice the yellowing, the claw, and nutrient lock-out. At that time, raise the ph of your ingoing water by a couple of decimal points, and watch for any reaction. (from 6.2 ph to 6.5 ph, for example)

Are you trying to use the test drops to determine runoff ph, and are you trying to adjust your ph accordingly...? If so...stop. You can not determine accurate runoff ph with the test drops. The tinting skews the color-coded results. Same goes with trying to ph the water after adding nutrients. My wellwater comes out at 7.9ish ph. I use phDown to adjust water to about 6.8 or 6.9, then add the nutrients. This brings down the ph to 6.2 or 6.3ish.

Are you sure you're not giving any additives or foliar spraying? (this includes the recent past) No Superthrive or tea's or anything you've mixed yourself...? Looks a bit like heavy metals poisoning, but I'd try maintaining proper ph before doing any other damage from poisons and crap.

When watering or feeding, are you sure you are getting water down to the lower root zone? If you never do, I'd flush well with properly ph'd water, as you might be getting salt build-up. I use Fox Farms nutes, and perform a monthly 'maintenance' flush just for this reason.