Struggling with nutrient issues (PICS)

I have a really old momma (3months) I used to clone that I am trying to get ready to flower. The soil is buildasoil living soil 3.0
I’ve been adding 5ml of cal mag per gallon and use about 1/3-1/2 every time I water. The light is a 630 cmh. I just transplanted to a 7 gal pot about a month ago. I water with ph of 6-6.5. Hopefully y’all can help me out. I really wanna flower soon but I need to get this crap under control first.

She is actually going on 4 months I think

Tbh
Get you some ocean forest... It's a lil hot.... So you have to really water in increments and graduate slowly to larger feedings but this won't be an issue

Imho

I’d like to just add some nutrients to the water and keep the soil I have if possible. I just am not sure what’s going on.

I understand your sentiment but it looks like you have a few things going on besides nite burn but I say it may just be the soil itself

Maybe you can try some with one plant and compare

Doesn't hurt to test

Hope everything pans out for you