Yellow leaves, comment only if you can help (had the same experience) , if not don't even type.

in photo number three we can see brown or red veins, it could be Fe deficiency. https://growmart.cz/wp-content/uploads/2022/01/deficit-konopi-growmart.jpg https://2fast4buds.com/temp/img_upload/bg_ab5cb20504befd4592c64c07a1142a1c.jpg

P and K deficiency looks different. I don't see any brown stains.

Starving............especially for potassium and phosphorous now they are flowering......... and nitrogen too. Generally under fed. pH is not the issue.

Well, you don't have a diary so it's impossible for us to tell you what's gone on - it could be the pH (but I don't know what pH you're maintaining), it could be poor watering practices (too much/too little), it could be a nitrogen deficiency (or a nitrogen toxicity which has locked out other nutrients) or heat stress or cold chock or magnesium deficiency or calcium deficiency or iron deficiency (this last is doubtful - coloring is not indicative)..... but to determine which is affecting your plant, we'd need more information. To answer the question of "why aren't all of them showing the same symptoms), I can only tell you that each plant is an individual and must be treated as such... it's entirely possible (and frequently seen) for the seeds of the same strain from the same seed bank bought at the same time to react to the same treatment/conditions differently. As an illustration, when I was a child, my brother got mumps.. my mother was desperate that I should get mumps then as well so I didn't risk getting it when I was an adult she forced me to sit on his bed playing board games with him every day (i.e., close exposure to the virus) - I didn't get mumps then and have never had them... but we were both the offspring of the same set of parents exposed to the same conditions... Plants are like that. All of that being said, when plants are of the age yours are, they start to require a lot more PK and a lot less N along with a good dose of calcium and magnesium... Make sure your pH is between 6.0 and 6.5 and add a PK booster as well as a dose of calmag (but only do calmag once a week). The leaves will never "green up" but the newer leaves should start to grow in greener and healthier.... if it's a lockout, though, you'd need to do a proper flush before starting those enhanced feeds. Good luck.

looking like nitrogen deficit. R u control PH water on watering?. It could also be iron deficiency, do you have NPK only fertilizer? You should also add some micronutrients.

My set up is 600W led at 80%, 55cm distance. Feeding with organic liquids that have npk. Good soil (mills lightmix). When I checked the runoff in the yellow plants it was a little high 7,1, but could this be the reason for lockout? Half of the plants look perfect green and healthy and all were feed the same.