Can under powering a subs blow them?

I bought 2 brand new alpine type r 10's and a kicker 300.1zx amp the subs are rated at 300-600 rms each the amp is 300rms I hooked them up sounded great for 2 days then just quit working I took them back and they tested the subs the channels or what ever you call where you pluge the wires in to the actual sub they read 0 ohms so he said there fryed I asked why they would do that he said my amp was to small is that really true or did I just get a bad set of speakers? Or is there something else there that did it