DARK Devil Automatic Sweet seeds

At the beginning of week 7 one of the three ladies started to develop purple colors, the other two plants show no color development so far. At the end of week 5, my largest plant so far started to show a deficiency and I then measured the soil pH value, it was 6.7 and I adjusted it to 6.1-6.3. I think there is a phosphorus potassium deficiency if I have understood this correctly They are also very thirsty! I'm still a beginner and this is my 2nd grow so far but it's so much fun growing these plants! I am really proud!