Nice gains buddy. Have you considered to add in deadlifting on your back day? Since on leg day you would be doing two huge muscle exercises.. deadlifting & squats. Or are you not doing squats? :)
Bro seriously lifting weights will not stunt your growth. Aslong as you use the correct form you will build muscles in 2-3 months. If that is all that you want.
Damn you are only 15? if you didn't include your age just from that i would be guessing you are 17-18. You have a really solid foundation there bro, especially when you get older if you keep this up...