Rust spots near margins on middle leaves

[blinken]

Long time lurker here, needing some help from some wiser folk. Not sure what's going on with this plant. I'm noticing this rust start to develop on the middle leaves of my plant. Any idea if this is a burn, or deficiency? Growing in promix, using gh flora lucas formula. I've not had this problem before so I'm at a loss, any tips would be swell. Thanks!

 

[mushroombrew]

Nute burn. It's on the tips too. What media you in?

 

[blinken]

Just promix hp. It's about 4 weeks into 12 week flower. The other plants showed burnt tips too but no sign of this burn on the leaves. Roughly the same size plants.

 

[mushroombrew]

What kind of ferts are you using?

 

[MJPassion]

Some of my OD plants look similar.
Since I haven't supplemented much K I suspect that's what my issue is.

From what I've read regarding lucas, you might need some Ca. Ca trucks the other nutes into the plant.

 

[blinken]

Some of my OD plants look similar.
Since I haven't supplemented much K I suspect that's what my issue is.

From what I've read regarding lucas, you might need some Ca. Ca trucks the other nutes into the plant.

Hmm, I flushed it pretty well and the rusting seems to have halted progression. Strange this plant did this, and not the others. I guess I'll have to wait another day or two to be absolutely sure it was an overdose.

 

[blinken]

Part of why this has me mystified is because, while the other plants have some lightly burned tips too, they are actually showing signs of deficiency with some of the bottom leaves turning yellow and forming brown spots. So I have most of my plants seemingly wanting more nutrients, but this one is burned? It doesn't make sense to me.

 

[MJPassion]

If the burned plant is a clone of one of the others, yes, not making sense.
If it's a plant from seed then results can vary dramatically.