First time grower need some info?

The first picture if you look at the far (left) leaf and the far (right) leaf. The (left) leaf in th top part it's starting to turn brown and the (right) leaf is starting to do the same on the edges though??? I have a LED light 60/65 watts almost 1000 lumens MG soil with fast release in it. I have the light on for 18 hr a day. It's been 21 days and the leafs are curling down to, How does the second picture look beside the brown spots???