Wtf is goin on need help Please!

Ite my babies are bout 6 weeks old bout go to flowering but one of my girls is having some major damage is going on with my fan leaves they are kinda changing colors but more starting with a brownish color coming out the veins then it spreads all over and the leaves just turn brown dry and die and it hasnt happened to the other plants just normal nutrient deficiency. I am using fox farms soils and grow big nutes i feed every other watering temp has been a stable 78 degrees with 24 hrs of light.... Good new tho my big girl is already flowering almost 2 weeks in and she is looking quite beautiful and im upgrading her to a 1000w this week so she can grow up big

I would start by a good flushing then waiting a day or so and see if the problem spreads. I have had this problem a few times normally it happens to me when I transplant if I am going to have a problem. If the flushing corrects the problem or I should say stops the problem from getting worse or spreading, then start adding nutes again at 1/4 strength and check your ph. Let us know how if this helps, if not then we can look for a different solution.
Happy Growing

Thank you will def try this cus i i did a sort of transplant just my bucket was lil low on soil cus of a spill and had to add more and it may have damaged the roots too cus they were not holding the plant securely in the dirt i also trimmed a couple leaves too so that it would try and develop more roots ill report back in a couple days

Looks like there are a couple of defs going on at the same time. My guess would be PH lockout.