Burnt? PH lock-out? too much Cal-mag??

Bad PH = Nutrient lockout buddy! But agree alot of key factors were missing in your diary, did you go from organic to synthetic nutes! Could of shocked or burned the roots maybe!

something is weird here, Its only affecting that one plant in the corner and your diary does not state how they are fed or what they are grown in, missing some key points. This looks like a burn to me but also a light to close issue. The lower leaves look to be affected by a lack of calcium. Some of your other plants in the tent also have burnt tips suggesting overfeeding and one of them has yellow edges on the leaves suggesting lacking potassium. You need to monitor the EC and PH of all 6 pots and make note of what they are. You also need to update your diary more often and with more info. I swear I've seen this photo before or one just like this. Good Luck!

Put something under your plant so you can get some run off water. Go check your EC and PH. In my opinion PH should never be higher then 6.5 in flowering state and EC 2.5 max, it depends on how big your plants are. If you have low or high PH with high EC, i should recommend flushing her with only water until you get the right EC. Because of flushing, she willl need a couple of days to get dry again. Make sure your plants are never dry or to heavy and keep some distance between your plants and lamp. Since your using LED and not HPS i don't burn by heat is the main reason.

pH water until run off check the ph it looks like she has more than one deficiency so I would guess she is in lockout because of pH issues 🙏