My man Doc shows his vast wisdom again. You will never see a reaction to PH in a few day's, more like 2 weeks. N seems to be another issue you have, as you are getting yellowing at the edges. Tap water, without adjustment, usually blows, so you have to PH it from the start and then you have a PPM issue also, as shown by the yellowing. In coco, PH is everything plus a mild nute solution which you should use a PPM meter to adjust your feed solution. Following the bottles instructions is not really the best, as PH will also affect that measurement. The plant appears to be young, so with adjustment you should be OK.
What I would do is test runoff and adjust as needed. I would bet you are in the 4's now, so I would flush the shit out of the coco using something like Clearex, test the run off again and adjust further. After the flush, you probably will be still low, so to get it into your target zone of 6.0 (foolproof) bring you PH up by one, so if you want 6.0 and you read 5.0, bring your solution to 7.0 to adjust back down to 6. Get it? You will be fine with a little fine tuning, so don't sweat it. You might want to do what I do with fucked up leaves, cut them off and forget about it. It works for me.