Hello
So usually with nutrient burns you'll see tip burn, the claw, and then it progresses. I don't see tip burn, but i do see some clawed leaves. So maybe Do a small flush, and then come in with less nutrients...especially your nitrogen.
Your brown spots could be the beginning of a calcium need...personally i saw a huge improvement in my leaves when I actively use a calmag supplement.
As for your lst...it looks good. Just keep it slightly loose so no branches break and keep on tying.👍