My stems purple? but watered good

Okay so i posted pics on my thing i read it can be the strain.. If you look at my post from yesterday the stem is purple but the leafs are smaller. It is bigger now.. since yesterday. So i don't think i should worry what do u think? Should i fertilize

I am on an iPhone so it's difficult for me to navigate pages but purpling of a stem is normal when they are first planted. They will turn kinda a purple green some areas straight purple. How old are they?

They are 4 days old =]