Odd Brown / Necrosis Spots

Hi All. I have looked through all the guides, including the one included in the Marijuana Growers Bible by Cervantes but I still can't figure this one out.

1) PICTURE OF PLANT *** VERY IMPORTANT ***
2) Growing indoor or outdoors
3) Watering schedule
4) Growing Medium
5) What stage of growth

1) Pics attached
2) Indoors
3) Every 3 days (when the medium dries out)
4) Pro-Mix
5) 35 days into VEG

I'll add
Strain: Grand Daddy Purple
Lighting: T5
Temp: 73-77 deg
Humidity: 48-60%
Pot Size: 3 gallon
Nutrients: Every watering. General Hydro 3 Step 15-10-5 mL/gal, with CaMg added in 1 tsp/gal once a week, SNS 209 added 7 ml / gal.
Other: Recently sprayed Neem Oil / Dawn Dish Soap on all plants.

Some other info, I have this condition on only 1 of my 12 plants this time around SO FAR. Last grow, I suffered the same condition on 3 of the 7 plants. These plants are flowering now with terrible looking leaves and much lighter buds compared to the other 4. As of this point, no other plants or strains in veg are exhibiting symptoms.

Thank you for looking!

looks like those leaves may have been light burnt and are just now shedding the damaged portion.

And the leaf tips look like you are on the verge of nute burn, these may be related issues if it can not be light burn.

Can't be light burn, this was always the shortest of the bunch (not it's fault, it was the tallest of it's strain sisters under different lights).
This seems to be happening to the old growth first.
I'll try a flush, but last time flushing did not correct the problem. If that becomes the general consensus I'll just flush it like a bastard and toss it if it never recovers.

Phosphorus deficiency and i just scrolled up to read your npk yeah it's K deficiency.

I suspected Phosphorus as well. But I thought - how is that possible everything is getting fed the same? Well, that obviously doesn't matter the canna works in mysterious ways as I have already seen on my last grow. I'll feed her a little more P, can you suggest a gH mixture that would work?

But I think you might misunderstand my nutes a little.
Remembering my current mix is
General Hydro 3 Step 15-10-5 mL/gal thats grow/micro/bloom nutes by the way, not NPK. Unless you calc'd the NPK using my numbers, in which case, kudos to you!

Thanks

Yeah i just glanced at the numbers but picture 2 had a thousand words lol

I'm changing my nute strength from 15-10-5 ml/Gal (gH formula from back) to 5-12-15 which lowers the N & K slightly but doubles the P to the same value (I think) as the lucas formula. Since I'm not seeing any other problems I'm not going to go all the way to the lucas formula.