My opinion would be calcium deficiency, possibly combined with some magnesium issues – the brown spotting between the veins and near the leaf edges? Or salt build up and lockup of secondarys.
Anyway you got a rather quick genetic. So perhaps don't mind and just push through the last ~2? weeks if it doesn't get too worse. Natural senescence is probably on the way or part of it.
Much more important would you pls. check your canopy like NoVC01 said? It looks more than shady and some flowers are looking squished.