Leaf coloring?

On my rdwc alot of the leaves are turning a drastically brighter green than the rest of them. This is happening on alot of my plants. What is the reason/problem for this? Thanks in advance for any help.

are your leaves becoming a darker green or like a lime green? if they are getting darker its prob N but if they are turning lime(ish) then it might be Mg.

Mg? What is that if you don't mind? Is it bad,and what can I do to fix it?

it means magnesium.
It's hard to tell without a pic though.
How old are they?

They are 3 almost 4 weeks old.

you need to get some calmag supplement

Is that compatible with gh's flora series?

I'm pretty sure it is. GH makes cal mag too.

Thanks I'll have to try that