Seventh week.
The plants had a growth spurt this week, stretching to 18 inches tall.
Day 45: There are still signs of nute deficiency, so I upped the feeding strength to 3 EC (1500 PPM).
Day 49: The vertical growth has finally stopped, they are putting all their energy into flowering now. The plant is drinking less water now
@Fast_Buds, I made a mistake when uploading the photos; from week 4 onward I confused the strain with another one. This is now solved and makes sense, since the Crystal Meth is the only one that could have the purplish / black colored buds.