How to maintain mass during basketball season?

My body naturally has a very fast metabolism. I am 5'11" and weigh 180 right now. A couple months ago I was at about 188. I notice that I always lose tons of mass and size after basketball season is over. During basketball season I basically hit the gym to lift Mondays thru Fridays except I also have 2 hrs of basketball practice or games each day Monday thru Saturdays and my only rest day is Sunday.

Is there any supplements I should take to keep my mass? Or should I just try to eat more?