Brown spots and yellowing

Overnight? growdiaries.com/grow-questions/86550-soil-ph More like building up problems for straight 9 days. I would suggest you refer to any answer to your question 9 days ago =)

Gehe sehr stark von Probleme mit dem Ph wert des Medium aus. Dadurch hast dir ne sperre rein geholt also Nährstoffe können wenig oder nicht aufgenommen werden von den Wurzeln

pH strips are plenty accurate enough for the context of gardening. No need for a 150 dollar pH probe and endless costs of callibration fluids etc. Really shouldn't need to do more than spot check once you have some good SOP. i don't think that much damage can happen overnight, lol. if it did, it's taking a nosedive super fast and won't just magically stop.. it'd be a total dumpster fire in 48 hours at that rate of decline. Not enough info. Your diary hasn't been updated in 12 days so we can't see any meaningful progerssion of the symptoms. What have you changed since your flip to flower... that'll be your prime suspects because the plants looked fine 12 days ago after 5 weeks of growth. though in your first week of flower, you woudln't have such developed bud sites, so there's some reason to be skeptical about the information provided. That's not 1 week into flower in your 5th week of diary. so, if you drastically changed the fertilizer formula or changed light intensity etc for 'flower', i'd look into those decisions and maybe revert some. chlorosis at the top could be too much p or k. could be overly-intense light. the necrotic spots are a bit much.. maybe overwatering? The symptoms don't seem to be in the right places relative to likely cause (mobile vs immobile). nute lockout or pH come to mind. easy to rule out pH.