Those are some gorgeous buds forming man, great work! I know you mentioned you couldn't figure out the nutrient burn. You also said you were just using tap water, this may be the cause, sometimes tap water can reach a pH as high as 7.3-7.5 at this point the cannabis roots struggles with what's called "nutrient lockout." This is because when the pH is this high the plant has major difficulties properly extracting the nutrients it needs from the soil. You seem to already be working on the correct solution though which is good to hear! Also instead of buying a synthetic one, an excellent (and cheap) pH down I like to use is citric acid! I find that just a pinch of it can lower the pH in my 15L water container by about 0.3-0.4! A little bit goes a long way with citric acid!
Thanks @justin2_m appreciate the comment and recommendations. Being my first grow I wanted to try to keep it simple but I think the pH is what got me. Bought a test kit and I think my tap water here is at least 7.5 if not higher. May need to try out your citric acid trick, like that it’s not synthetic.