vocal mic has gone quite acoustic guitar goes quiet

I am using a Europower Pmp 2000 and a pair of B212 speakers which originally came together. When I am performing singing and playing guitar my vocal mic has cut out or gone quite and my acoustic guitar goes quiet. I even press the pad button to reduce the db but that doesn't stop this happening. Could this be because the speakers are either old, have a built in protection function, too small or not powerful enough??? The power amp is 2000 watts and the speakers are 500 watts peak each