Hi, Honestly?
Kinda poor for that old. In all respect you should be looking at what is off in the grow. What is your seed 'tap' root connected too; is it rockwol or just your expanded clay? BUT they still look green just not vigorous. U kinda get to see vigorous signs by large leaves and longer stocks on seedlings for the first bit of growth. I dont see either in this case. Maybe just the light? BTW I like it that its clean! Everything I said is obv in respect; so a recap, look a little behind but not unhealthy. Just held back by something. either light or rooting medium I think. U prob have to water the expanded clay every day two times a day if you have no rooting medium?