Week 3 Blackberry feels much better than Green Crack.
day 15 - i got some problem with Green Crack. Leaf becomes yellow. Corrected ph and waiting.
day 16 - Green Crack still loking bad. Still don't see roots.
day 18 - Still no progress with Green Crack.
day 20 - finally got new leafs on Green Crack. Still little roots. Looks like my mistake were in nutrients.
What types of lights are you using? Your plants are very small for 4 weeks old and have stretched a lot. Are you checking the PH of your water ? It looks like the leaves are yellowing from either lack of nutrients or wrong PH.
I’m still learning myself. Look at my diary for similar 4 weeks age (under week 5)