There’s nothing wrong with plant other than roots air pruning itself. Is that the cause of this ?

Plant has outgrown the pot long time ago.

Por mi es un problema que falta Mg o no tiene acceso a Mg.. Alto livel de P puede causar un bloque en el acceso al Mg

This is nothing to do with the roots "air pruning" and everything to do with feeding/nutrition.

Looks like she lacks Mg, Google it, it's similar to a Nitrogen deficiency but has the red stems with the dark green veins on yellowing leaves. Weed plants do not need a lot of Magnesium, but if you use Coco, the coco will actually "steal" away Mg by binding to it, and not letting go. So you want to feed a little bit extra, to overcome this, that's what we call "Buffering coco" Find a decent CalMag agent, make sure you are below 6.5 but above 5.8 ph and make sure you are not locking the plant out of mg (Overfeeding will cause this for example) Air root trimming is fine and doesn't hurt your plant, compare it to clipping fingernails.

Discolered probably by nutes... doesn't look infected or anything. Yeah, that's normal. they'll bore through fabric and they will air prune themselves. As far as the plant, i can't really see the leaves to help you there... and, regardless, find a decent 'marijuana leaf symptom chart" through a google image search. Get familiar with it.. notice difference between mobil and immobile etc etc.. it's a bit of art mixed in with science, but overtime you get familiar with it and recognize stuff easily on your own. In diary i see Mg-deficiency -- interveinal chlorosis starting on middle leaves.. bc nothing else is coinciding, i'd feel safe this is accurate conclusion. Mg deficiency starts 4-6 weeks before onset of visible symptoms on leaves. If S isn't high, epsom salt (magnesium sulfate) is an excellent option to boost Mg without significantly throwing balance off of other stuff... (besides Sulfur, obviously) the more convoluted teh symptoms are the more likely it's pH or lockout (ratio of nutes given) related

I'm not understanding your worry here. Yeah, the roots are growing out of the pot. That's completely normal - they're obviously very healthy roots and they're being air-pruned.... doesn't affect the plant at all.