Happy with growth as such but I’m concerned with the reddish purple stems and the colour.
I have this problem often and still not exactly sure what it is, if it’s anything at all.
I will be watering with PH 6.4 water to see if it’s struggling to uptake magnesium.
They are actually good. At the begninnin they never get the intense green. I advise anyway a spray of algae and fulvic acid. If you are following the schedule, the problem could be pH too. Anyway I wouldn't be too much concerned
The stressmark-spots could indicate ph fluctuations, as they result from bad nutrient intake. The overall light greenish tone and purple stems could result from low Mg levels. If adjusting ph isn't enough any CalMag nutrients will do.