What is the problem ??? Nute burn? Calcium or magn...

Your feed and your plant is on point you do not have no kind of deficiency the only reason your bottom is turning YELLOW is the lack of light its getting thats all 99% of every plant will do this if you had the problems that are listed in this your plants wouldn't look as good as they do u got wat 4-5 leaves just clean em up and keep rolling homie i would change nothing 👍👍✍️✍️✍️✍️

The first 2 leaves on that video show clear symptons of potassium deficiency, the 3d leaf has shows phosphoroust deficiency. What your plant needs is more biobloom nutes and at this point, reduce or just stop using biogrow. There might be some over watering too, careful with that. I would increase the magnesium too, since you can see as some inter veinal yellowing (very little at this point), Epsom salts would be best, if not cal mag will do.

hey you have signs of Mag deficiency. What i suspect happened is that you overwattered slightly one time, made the nutes a bit more available than usual which led to a minor lock out of these nutes + based on the 20h light schedule, the plant has gone into overdrive during bloom and needs way more magnesium. The leaves won't recover, but as long as you strictly follow a wet dry cycle you should be fine based on the quantity of nutrients you're already adding. This too will pass my friend, good luck ! 🚀

So from what im seeing in the video is that your plant suffered from a couple different things here CalMag , phosphorus and potassium . I can tell its a combo of the three because of the way the plant is gaining spots on her leafs and curling . The yellowing and the browning spots coming from PK deficiency. From your nutrient chart that i can see here you need to boost the PK really hard you are using more grow then you are bloom . Your plant does not need more nitrogen at this time it needs potassium and phosphorus to facilitate the bud development on new site and current ones . I would also add CalMag to your feedings I can see it in the picture that your plants needs it on the leaves you can see the yellowing in between the vains of the leafs this is a clean indication of cal mag deficiency . So i would remove those old crusty yellowing up leaves fix the nutrient solution to be more bloom oriented and add a little CalMg if you chose to follow this your plant will return to a nice healthy green and keep on prospering ! -Happy Growing!

i its a typically picture of Phosphorus defiency. Your plant is in Flowering Stage and she has a big need in Phosphorus and K now. Your leave shows the Typically sings of that. This damage of the Leave wont mend again but you can give your plant any Blooming fertiliser/ booster of you choice because they have a bigger amount of p+k into it. Your plant had also an Nitrogen def , when she shoots into flower, she just cannibalised herself and such the N out of the Leaves but that is now no problem. just pick awy the wilting leaves and give your Girl some Phosphorus for the flowering.

I will start with one normal fact about plants: older leaves that are not reached by light for a long time get "recycled" by the plant, she try to take back all the mobile nutrients and she let the leaf dry out. Is similar to the autumn process in deciduous trees. You should always put a full plant picture/video when asking for this kind of questions :)