hi, well i reckon m8 that the soil was just a bit hot, clones are mad anyway i reckon that even tho they come from mature plants they still need a cooler soil to start with, but at the same time once theyre established they can get hungry, but your soil should be good for maybe 6 weeks its hectic i know but sometimes i reckon youve just got to let them sort themselves out, all the time you have new growth and the burn dosent get out of hand then youll be ok, remember you cant repair burn but you can stop it,
the purple stem thing is mad aswell as some varietys have blue in them and hence youll get purple stems and bud, also cold temps can do it, but in general its when a leaf has reached full maturity, as with yours its the lower ones i noticed, and of course theyre the older ones, so nothing to worry about, the fact both are showing it is in one way good as it would point to something they both have in common ie soil, food,
good luck
cozz