What do you guys think?

the 2 plants have red stems, not a genetic trait..and I keep getting these burned tips...pH is not off..around 6.5
I'm using 1/2 strength, so not over fertilizing. Had this on my 2o grow..thought it was over fert, but now I'm sure it isn't. Is This P def?

Thanks!

magnesium deficiency? I see nothing wrong in the last three pics, but that first leaf looks like mg

i grow in coco so not really my field.first pic id say cal/mag, can see tip burn in the rest so maybe u locking cal/mag out due to salts or and ph check with soil growers.

What nutes are you using? How well does it supply cannabis's needs? Are you using calmag? That plant looks beautiful! And happy! I don't think you have a big problem. If its only affected one leaf I wouldn't worry. The most I would do if I were in your shoes is flush no harm in it, flush with ph corrected water get the salts out then just go back to feeding like you we're. Purple stems should be caused from cold night. Your always gonna lose leaves you just have to know whether or not its natural or a problem and by the look of that plant I think It doesn't need that leaf anymore. I would be more afraid of over reacting and harming the plants health.

I started 1/4 strength (the brand isn't well known "Wondersol") cause the plant is 3 weeks old. Thought the nutes in the soil would last a bit longer..maybe it's only hungry.

You're probably right, KIR. That's the 4th real leaf before I fimmed it
"If it ain't broke, don't fix it" Got it! thanks

This is usually caused by either- pot too small, moisture stress (pot drying too much), or ph out.