Potassium or magnesium?

Hi everyone, I currently have 4 fast buds autos on the go in bio bizz lightmix soil in 6.5l pots. I'm using the bio bizz nute line under a mars ts1000. My leaves have started yellowing on the outside in on one plant, and the other in going yellow between veins. The remaining 2 have very thin twisted new growth. They are all 29 days above ground. Is this a potassium / magnesium problem?

Maybe a PH problem causing the magnesium to become unavailable. I saw this type of leaf “clawing” in my THC Auto Bomb at night time. It started right at pre-flower stage. It turned out to be high PH in my organic soil. The recommendations I received was to feed lightly every watering because the organic nutrients helped bring the PH down. I am still struggling with the PH. I also added a 1/2” layer of worm castings. My plant still is not reaching for the sun but parts of it isn’t as droopy anymore either. It developed a lot of discoloration.

Do you think a good flush then start with quarter strength nutes. It's odd as I've pH my water to 6.5 every time

Potassium and sulfur. The pics of the fan leaves show k def. And the leaves at the top of the whole plant pic show sulfur def. Looks like you could use some mg based on the purple leaf stem. Epsom salts will fix both mg and sulfur. Bloom nutes for the K.

Cheers, I've been feeding right and including calmag but I reckon my soil pH must be outand plants aren't uptaking the nutes. With the epsom salts how do I apply them