Potassium deficiency?

Phosphorous deficiency, not potassium.

K-def usualyl goes around the serated tips before the center parts of leaves... if this started out as interveinal chlorosis, i'd look to Mn, Zn or Fe... which would be rare and hints at pH issues more often than not. where it starts on plant and how it progresses are all bits of information to eliminate possibilities. This is also something that's been happening for a long time at this point, so you need to react sooner. Once you are confident about where it started and how it progressed consult a leaf symptom chart and play the best odds. Simple as that. Keep asking questions, but start deducing what is wrong on your own to learn the symptoms. A good chart explains mobil vs immobile to help eliminate possibilities. smorgasborg of symptoms or unusual symptoms in the wrong spot hint at a nutrient locking things out, pH issues, light damage or watering issues (pH is really part of watering). waterlogged roots will cause damage originating from veins too.

Yeah, I think it's a nutrient deficiency, either not enough fertilizer or a nutrient lockout. If your pH value from the runoff isn't between 5.8 and 6.8, it could lead to a nutrient lockout, and then your plant won't absorb anything even if you fertilize it. I would check that first, then also the EC value. If it's over 2, you have too much salt in the soil, which can lead to the wrong pH value, so check that too. If everything is in the green zone, just keep fertilizing. If the pH is off, give it pH-adjusted water, and if the EC value is too high, you need to flush with water. First, do it properly, then after 2 to 3 days, check again. Keep measuring until everything is okay.

Hey there my guess is the soil ph is slightly off and you saw some signs of that and you started to give less nutrients now you have slight signs of the soil ph being to low and on top of that you are starting to have a lack of nutrients leading to the plant to kinda canablize itself…. Its not that bad of a thing it’s just the plant taking energy and nutrients from leaves that are not needed and moving them to bud formation The solution would be to check the run off water ph next time you water it will probably be low down around 5 or so you will be able to just run a few gallons of tap water if you tap water is ph 7 to 8.5 that’s fine you can use just plain tap water to bring the ph back up just a little.. even raise if the ph .5 does a whole world of a different to being able to absorb nutrients and stop getting acid burns on the leaves Honestly if your at week 7 or 8 of flower don’t even worry about the lack of nutrients at this point if you fix the ph and maybe hit the plant with one or 2 more good rounds of nutrients b4 harvest. Don’t focus on trying to give a bunch of nutrients to bring the plant all green again that is not gonna happen there is not enough time b4 harvest Your plant is not gonna die even if you keep doing exactly what you’re doing. When you get to the final stages of flower it’s really hard to kill a plant Good luck

From the pictures alone, this looks like a potassium-related deficiency. The lower leaves are yellowing evenly with signs of edge crisping, which fits late-flower K hunger. It’s common in week 7–8 of bloom, especially if the plant has been running without nutrients. Looking at your diary, it seems you've stopped feeding for two full weeks now. That might have pushed her into a deficiency — especially since she was getting regular bloom feed before. At this point, she’s likely running low on available resources to finish strong. You don’t need to restart heavy feeding, but giving one light dose of bloom nutrients could help stabilize her until ripening is done. She still looks on track to finish well.