3 weeks flower white rhino leaves turning brown and black ? help please pics inc

hi ive got a problem with my white rhino growing in plain gardencentre soil with biobizz nutes only using half dose under 600w hps(which i did have a bit closemoved higher now tho) but in the last week or so the leaves have started turning brown speckled and some black at the tips ive only just got a ph meter and the water was 7.5-8 is this what has caused this ? or is it something else help plz

anybody ?

someone should answer this question, and i have no idea.

possible nute lockout since ph is high, looks like lack of phosphorus. i would lower to 6.5 and see how they respond

Some of my lower leaves went like that cause i got some biobizz nutes & water on them when i was feeding them.