Leaves curling up with brown spots! First grow :)

[Oggstar]

Hello, I am new here and I hope you guys can help me. I am currently in the middle-end of the flowering period for my first serious indoors grow.
I am growing two easy bud and two royal dwarf from RQS but being a noob made me mix up the seeds so I have no idea which one is which. Lol.
My grow has been full of noob mistakes, especially in the beginning of the grow. Overwatering, underwatering and overfeeding are all problems I have encounterd.

So now to the problem, today when I woke up I noticed that some of the leaves on my smallest plant have started curling up and they are feeling kind of crispy and having dark brown spots. The spots look like the spots you get if you spill nutrients on the leaves. But I did not give them any nutrients. Just a spray of water to keep the humidity up.

I have not tested PH since I have yet to receive my ph tester...

What could be the problem and what should I do?
Most of the problem leaves are in top, but not exclusively.
I hope someone here can help me, thanks!

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[cornish smoker]

Rust spot could be a cal/mag diff. If you think you have added to high nutes then I would give them a little flush.
I'm sure someone with more experience will be on in a second will be on and can put you right.

 

[DreadHeadiez]

Looks to me that your girls may just be hungry for a little Phosphorus and a bit of Cal/Mag.

When was the last time you fed ? What are you feeding and how much?

Doesn't seem like to big of a issue. Next grow I'd add a extra source of cal/mag. Dolomite Lime is what I prefer and it's a great pH buffer in soil as well.

The first two pics display reddish/purple stems and purplish in the foilage itself with necrosis which makes me believe they're just a bit hungry for Phosphorus .

 

[Oggstar]

I forgot to mention that I recently got a new LED lamp.

But yes, after looking up phosphorus difficency I think it might be it. The nutrients I use seem to be low on phosphorus too. What do you recommend I do? Find new nutrients? Or should I add something else for the phosphorus?

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[Waira]

-- hey mate, how far away is the light, and what type/model? These are mixed symptoms, likely just what was mentioned above-- Ca (finer spotting) and P (larger necrotic patches) defc.'s,.. but we need more info please,... look above this section, there's a highlighted "sticky" threads section there; you'll find a patient form to fill out, just copy and paste it here and fill in the info so we can put a fix together,...
...don't bother with dolomite, it's the slowest acting form of lime, and lime in general won't work fast enough, you need a liquid Ca-Mg product with right-now available Ca/Mg,....
... best thing for soil/sloiless mediums pH testing is a pH probe, for actual in-pot measurements,.. Accurate 8 ( by Control Wizard) is a good model, not too expensive,.. i think the identical unit is available in EU, under a different name-? On your version of Amazon,...

 

[DreadHeadiez]

@Waira is the plant dr on here man. Like voodoo with this type of stuff. Youre in good hands now.