Hi! I am pretty new to mining BTC, atm I have 2 miners that are working pretty damn slow (15-30MH/s), one is fine and solves algoritms normally, but the other one just runs at 18MH/s without solving anything  I really don't know what the problem could be, please help! 

P.s I use 50btc.com's pool togeather with 50miner.