Hi,

I recently just purchased a couple of these myself to run along side with my other USB miners.  Chances are its like a couple posts have mentioned- power.  I have a bi-fury at home that I fought with all day until I finally used a bench PSU and all problems were solved instantly. The ant miners I picked up seem no different, they are just hungry for power once you start hashing. 

Have you tried only running the two? do they both hit their target hash rate?