what happen and how to heal

mottling on old leaves - it can just happen, but i'm guessing overall health is a factor too? and what i would guess as a Ca deficiency = rust spots with no interveinal chlorisis. purple petioles (leaf's stem) can be a P-def -- also, can be from LED lighting, if oyu only see it where exposed to greater amounts of light - i.e. near top / gaps in upper canopy allowing light through. purple streaks in the stem is Sulfur def. So, depends what you mean by the burple stalk. I wouldn't suspect any lockout based on asthetics, but do ensure pH is somewhere near proper range too.