I had this too once with one plant,
I think it is not incorect ph, your PH is like 5.8-6 which is good for growing.
I can't see your PPM/EC on your diary and what kind of nutrients you gave her so my advice will not be 100% :(
It can be a kind of milddew ( there are like 2 of them)
You can fix that with spraying her with 900ml water mixed witth 100ml milk, but for some leafs it is to late.
Make sure when you spray them, your lamps are off.
Also turn your leafs and see if there are little insects running beneeth your leafs.
Last time i had the same problem i also had some insects like spider mite.
Your leafs also give me a overfeeding vibe, you should flush your plant a bit and check on your run-off.
If your run-off has like more then 2 EC in it, you have overfeeding her as well.
Good luck growing