Northern lights automatic- 250W HPS

This gal is going great, growing in height and beatiful flowers starting to form. The last week i've been giving it water corrected with vinegar( to achieve ph 6). I bought some biobizz nutrients this week and gave it some bio bloom and top max. But I noticed after a couple days that the top bud leaves are not upright as they should and the color on the leaves is starting to change. I did a small flush just in case it's excess nutrients, let's see how it goes. I've eliminated excess heat and lack of water as potential suspects. What do you guys think?