Leaves are getting more and more yellow, should I ...

I am repeating what the others told you : 5.8ph in coco is the sweet spot

I had a similar problem. I grew with ph around 6.4 - 6.5. Then i adjust and hold PH on 5.8 - 6.0 and the plants get better soon.

You are watering at 6.5ph ? in coco it is advised to water at 5.9ph, this could solve everything. I would flush out and continue watering with adjusted ph levels, if no change try increasing the grow nute. 🌱👍

Yes you should be worried... I believe you may have a nutrient lockout situation.. Nutrient lockout will resemble nutrient deficiency. Any yellowing or curling of the leaves also indicate that the plant is experiencing nutrient lockout. Your cannabis plant might be oversaturated with nutrients. If you don't flush, it might only get worse.. Keep in mind different plants sometimes need/use different things. So you may have one plant that reacts fine and another plant that is being overfed. If I was you I'd just flush for a few days then go back to lighter feeding of like just overdrive and floracoco bloom cut out the grow and big bud. I like using big bud myself but I have found with base nutrients it can be rather strong. I know of people using just big bud during mid-late flower and nothing else.. Big Bud is almost a main nutrient in itself.. Iv'e found a lot more success with the Advanced nutrients line by using 1/2 what they recommend.

Browning tips are normally a sign of to much nutrients (nutri burn) and the yellow/ brown spots are normally a calcium/magnesium deficiency. Don’t know what you growing in but a flush and drain is imo a good start and refill res with lower amounts of nutrients. Also get some cal mag. Just my opinion bro. Hope it helps.