i also got my 2 bottom leaves curly and darker...but im not worrying about it since the plant looks so healthy and grows fast . you shouldnt either your plant looks amazing! lets hope its a gal!
This plant turned out to be male so I chopped it down a while ago. Don't worry about leafs curling up a little, I can say now I got some more experience. Just keep an eye on them and make sure it doesn't spread up in quick rate. Eventually bottom leafs will start falling off...completely natural.