Nute burn or Potassium deficiency? Or something else?

DWC going on 6 weeks of flowering. Using Botanicare Pure Blend Bloom, LK, silica blast, and Botanicare sweet. Ph stays between 5.6-6.0. Temp between 75 and 80F. Humidity around 50%. Only lower leaves are affected. TDS around 1150. Here are some pics of the affected leaves, buds on plant, and a pic of affected area. Thanks for any input!

So is that only on the bottom leaves? Or is it spreading all over the plant?

Reminds me of fungus/mildew damage almost, but I have no idea atm.

The tops don't look burnt or anything and it's around the tips and edges of the leaves.

I am sure someone who has more knowledge will pipe in soon enough.

Its more on the bottom leaves kinda spreading up to the upper ones.

so i looked at the damaged leaves under a 60x loupe and i can see like really tiny white spheres/dots like where the damage is furthest from the tips. (almost like they are making their way to the stem because the browning appears first at the tips and makes its way to the stem along the edges.) couldnt get a picture but is that some type of fungus/mildew?

More damaged leaves i just cut. They start on the bottom leaves but slowly moving its way up the plant.

Check for aphids too mate. That looks similar to what happens when those little pricks leave honeydew everywhere.

I dont seem to see any at the moment. i looked all up and down and underneath the leaves. but no bugs. is there anything else that can cause this necrosis at the tips and edges with the leaves still dark green??

Mabey excess nitrogen is blocking the potassium

That might be possible because a little botanicare pure blend grow was added with the pbpbloom because leaves were yellowing up a little too early.

Root Aphids? You wouldn't necessarily see anything other than a slightly sick plant that drops leaves.

Im at a loss lol. I guess just let it go a little longer. They should be almost ready for harvest within couple weeks