HELP! Nute burn?

[YYCannabis]

First time grower. I have 2 of my 4 plants with yellowing of the lower leaves. I think it’s nute burn, but I’d love for an experienced grower to provide feedback.
Also, in the one pic you can see the stem of the plant has little white bumps. I don’t know if that’s normal or a sign of stem rot.

Cheers
YYC

 

[Rwise]

The white bumps are roots trying to grow, I would cover them so they can!
They need/want bigger pots,,,

 

[YYCannabis]

Thanks Rwise. I will have to see what I can do about that.
Any thoughts about the cause of the yellowing leaves?