are you able to tell me if those subs are DVC or SVC....DVC means that there are 2 voicecoils. when you look at the subs there will be 2+ and 2-. SVC with just have one of each.

then can you tell me the model number of that amp.

maybe the subs are wired in // bridged on the amp and the amp could not be stable @2OHM bridged.