looks like you locked out mag
didnt mention at what ec rate your at
purple stems and yellowin the leaves
myself id drop the mkp and get back to just plain jane feeds and let the plant heal
if you gonna spray or foiler feed them ,use epsome salt instead,i really think you op need magnesium not calcium,1 tbsp of epsome to a liter of water .would a spray of cal mag do any good or does lock out prevent cal mag from working? Thanks.
The burned edges are from too much K, and it looks like its generally overfed.. glossy leaves, signs of fert burn nd subsequent lockouts etc..