Why are the leafs on my plants getting dark green ...

Check your leaves. If they are curling and/or clawing it's nitrogen, look for it in the Newest growth. If your leaves are shaped "right" then it is not nitrogen and they are just dark.. Without seeing nice and clear pictures of a "problem" plant it's very hard to tell unless they are suffering badly. From what I can see they look totally fine, if there is clawing/curling it's only minor. You don't even need to cut the Nitro out altogether you just go lighter on the feedings if they indeed have slight toxicity. Lots of growers just do very "light" feedings every time they water. The plants need the nitro right now and will eat it up just don't wanna oversaturate them, if it is indeed a case of slight toxicity. You are in Great shape really if it is a nitro tox, you've got plenty of time before flower so you can really get your plants dialed in before you flip :). I hope this helps if you need further information please pm me I can help :). Happy growing.