Keep getting nute burn

[Lazarus13]

So im running into a problem. I am in the beginning of the 5th week of flower on a white widow strain. 2 plants in a 5 gallon dwc. 2 300 watt old style mars hydro lights, AN 3 part ph perfect with big bud, voodoo, great white, sensizyme and humic acid and calimagic. I've been running everything at slightly under 1/2 strength and have been getting just the slightest tip burn. At my last rez change 4 days ago i cut it down to 1/4 to see if it would get better and it has gotten worse. About 3/8" of my leaf tips have burnt and have a slight curl. Should i go even lower? Flush and just let them have water for a day or 2? Take out the big bud?
Ph is staying between 5.8 and 6.2 and ppms were low 800s when i changed out.
Getting close to harvest time and i dont wanna lose it now. Thanks people of 420 in advance.

 

[Lazarus13]

Figured it out. What i was mistaking for nute burn was a potassium deficiency. Changed out my res and added a p/k booster and everything is right as rain.

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[Planter420]

Would like to see two plants in one five gallon!