looks like bugs to me, i would have thought the outer of the leaves would be affected before the inner like that if it was a ph/nute problem.

check the underside of the leaves with spots, any eggs or bugs of any sort?

wen my plant first had spidermites ther was no webbing visible, when u can see it, theyl be starting to overtake the whole plant.

if ther is no bugs, try using strait water for a bit and see if it improves?