leaf colour, purple edges.... normal or no?

Hey guys I was just wondering if anyone has an opinion on these leaves on my one big bud plant.

It is about 4.5 weeks into flower.

 

This is one of 3 I was not able to move out of the small small pots, so I am constantly struggling to keep them from going dry

 

I thought that would be Nute burn so I was watering only with PH water but you think it’s a PH prob? I always water with ph’d water 6.5

 

I will right now

 

Distilled water read 7.0 before test with 1 : 1 soil and same distilled water , filtered and then assessed with PH meter and read 6.6 on my meter for slurry test.

I have not calibrated with the given solutions but I have compared with a known PH source and it always reads good. When I adjust PH as I normally would for my feeds my meter always responds what seems appropriate for the ML of PH down I add

 

Another pic of the entire canopy of affected plant , it should be clear which one we talking about

 

Does anyone else have any experience growing big bud?

I feel like it isn’t reaching close to its potential due to size issues and keeping it in a small small pot when I flipped the rest of the grow to 12/12, not as much soil to act as that buffer....