I do not grow from clones so it would be best to listen to the advice of those with a good amount of experience growing from clones but when you see purple color on leaves like I see in your pictures that can be caused by a phosphorus deficiency.
If that is the case you will see slow or stunted growth, red stems, dark or purple discoloration on the leaves, smaller leaves that are dark green, lower leaves yellow and die. The fix is to add chemical fertilizer containing P. The affected leaves will not show recovery but new growth will appear normal.
 
Phosphorus (P) is necessary for photosynthesis and works as a catalyst for energy transfer within the plant. Phosphorus helps build strong roots and is vital for flower and seed production. Highest levels of phosphorus are used during germination, seedling growth and flowering. Deficiencies will show in older leaves first. Leaves turn deep green on a uniformly smaller, stunted plant. Leaves show brown or purple spots.
Now it may be something different so wait to hear from enough experienced clone users before doing anything but in general when it comes to herb plants a dark/purple discoloration on leaves is a P problem and not from an excess of it.