Leaf edges brown, Potassium? Calcium? Magnesium?

I first noticed this about 1-2 weeks ago, when I got lazy with my water and used tap water for about a week. I've gone back to distilled water but just wanted to see if this was something else that happened coincidentally...

8th week of flower - Big Bud Sensi Seeds
Using GH Flora Series - DWC system

My PPM was up around 1000, but thinking this could be nute burn I drained a couple gallons of water and put in regular distilled water to bring the PPM down to about 500-600...

Any ideas what the deficiency is? Should I just lay off the nutes for a bit? I actually just got some cal-mag in the mail the other day, haven't used any cal-mag all grow... should I add any of that?

By looking at the trichs on the plant I'm guessing I'm still 1-3 weeks away from harvest... Any input is appreciated.

p burned during bloom, If your close watch those trichomes, no sense in trying to cure a finishing plant. secondary macros, are as important as primarys npk the plant will grow to full maturation with what is in most comercial feeding programs, check to see if your supplement secondarys that just arrived has (S) sulfer as well it is also important however, may be in your part (a) instead of the supp pack, also accuire a micro nute pack. Once again, your plant will grow to maturity with out it. But the reasults will not be as good these are essential for a good healthy plant. looks like the burning is from a slight p overdose. looks like they are getting ready for a finish.

P? Phosphorus? First grow here so I'm learning the ropes... So with the gh flora series, I would imagine that P would be in the bloom solution as oppose to gro or micro... So in this instance, backing off some on the bloom solution would be advisable... I had been doing 20ml per gallon of water... I'm thinking 10-15 would have been better now...

Can anybody confirm my last post? Just want to be able to make the necessary adjustments next grow.

Concentrate on bloom nutes and take her accross the finish line!

That's where I'm at right now... about 7ml of micro per gallon, and I was doing 20ml of Bloom per gallon... But if this is P toxicity then I would imagine I would need to back off the nute that is providing that... which in my mind I would think that's the bloom solution... So I should lower from 20ml down to 15ml? 10ml? Or is there something else completely that I'm not thinking of. I swore the tap water did this, but I'm exploring all options.