They are back to health and reaching for light. Lookin' good. When you have time to go to a grow shop and pick up a real cannabis fert, do it! Then you won't have to worry about imbalances as much. The purple is likely a combination of 2 things, and to understand it you should understand WHY cannabis plants turn purple at all.
They are capable of producing several different pigments, and can be red, orange, purple, yellow, maroon, grape, and every imaginable shade of green from lime-green to almost bluish green. They can even be albino or variegated.
The basic green color is dominant in a healthy plant, because of the chlorophyll it uses to photosynthesize.
If the chlorophyll breaks down for any reason, typically cold or Nitrogen deficiency, any other colors that the plant produces will show through. In your case, running 'purps', the plant is genetically capable of turning purple and wat yo uare seeing is that particular pigment, unmasked by absence of chlorophyll.
Later in flower is when you should see that. Until then, keep those babies GREEN!