Purple Kush at 4.5 weeks - Leaves turning brown/yellow?

[ktznj4]

I topped this purple Kush 5 days ago. At the time the leaves in question were already yellowing / turning brow slightly. A couple days after topping, I changed the nutrient solution and the browning yellowing leaves turned worse.
After changing the nutes, the PH flew up from 5.8 to 7.5 overnight. I took it back down to 6.0 and it crept to 6.5. I thin I've got he Ph under control now.

Could this be a Manganese or a Magnesium deficieny?

Thanks very much all

 

[Peripatera]

It started with nitrogen toxicity and light+heat stress help the leaf burn 2 attackers on one leaf.

 

[Complatict]

I agree and you may solve it flushing than keep it untill it becomes dry.