How do I see it : with my eyes !
How do plant grows : thanks to the roots they are feeding and thanks to the upper parts they are breathing !
Ok it's not even funny so they are healthy even if I think they are a bit light green so as you are in the 1st week of flo she'l need an extra Nitrogen to achieve the stretch without any deficiencies , a feeding with veg nutrients should be enough.
Your plants seems to grow without issue , the stretch is starting so they should double in size before you'll see the first buds