Day 21 Leaf Discoloration

I think @Chubbs is right. It´s an effect of overwatering. Peace 😎

if u fed her then K excess and lockouts of other elements

May not be a deficiency. Without knowing how much you’re feeding and how often you water it’s hard to say. Do you water everyday when they do not need it, or let it dry out too much. Do you feed with every watering. How much run off do you allow, etc. Make sure your PH is correct, for soil it’s between 6-7. If it’s not right you’re guessing at what is wrong. I understand some experienced growers will go 24 hrs light cycle with autos. It’s hard on the plant and I would not recommend it. The most I grow my autos on is a 18/6 cycle and they seem to thrive in this both in flower and veg.

If you're thinking about the lower leaves, then it's normal, the first set of leaves function is to start up the plant, later they die and fall off, like booster rockets :) However, it looks like: A. Your soil is too dry B. Your feeding too much Nitrogen (burned tips)

Not a deficiency, but burning from feeding too much or too often..........or both. Try filling out your diary completely, the more info, the better the answers to your questions. Also, never, never grow at 24/0, all cannabis plants, autos included, NEED "sleep" for a correctly functioning metabolism. A plant with an incorrectly fuctioning metabolism will always have issues and will not reach its full potential. 18/6 is optimal. All cannabis plants NEED a daily photosynthesis cycle, there are certain processes that can only occur during lights out that the plant NEEDS to do that it can not do during lights on time..........that is why they NEED "sleep". The MYTH that it is ok to grow plants for weeks/months at 24/0 is absolute bs.

From the yellowing down down at the bottom it looks like it might be over watered or possibly not allowing enough dryback between watering. I've grown that strain many times and at the stage your in I wouldn't be feeding it more then 500-1000ml a day depending how much it drinks.