Hey all, Me again, here is a picture of a two week old cutting, just noticed some random rust looking spots on the leave...doesn't look like nute burn but I could be wrong..take a look
it could be nute burn the only thing you can really do is give it a good flush and see if that helps some
6.0 is pushing it on the really low side for soil, specially FF, 6.6 seems to be the best p.h. and I'm sure other soil growers will agree within the range of 6.5-6.8 depending on the strain, anything out of that range you start getting nute lockouts which can also lead to certain nutes still Able to be absorbed, create a buildup/ burn within the plant as all nutes are needed in unison to use eachother up. My suggestion bring your p.h. up and things should start looking up
If your PH is 6.0, thats entirely fine. Did your light fall on those leaves or did those leaves get trapped against the light somehow? IMO, that def looks like the bulb scorched your sun leaves.