Dark leaves

Hey guys I have three 3 week old marijuana plants day are starting to look a little dark and the edges of the leaves are starting to get shiny not a waxy shiny like a purpley shiny the plants have Healthy Growth but they still seem to stay dark and they have shiny speckled to them on the sticker Leaf Indica plant some of the leaves are starting to bend at the stem but the leaves seems strong still the stem is the only thing bending just happened very recently when I turn the humidifier on for a bit I am assuming this is probably because they got heavy from the water