could i solicit a little help on this?

A few weeks back, the tower speakers went out. started looking and found that the amp was in protect mode. I turned off all power at the main breaker, tried to check all wire connections. everything looked and felt solid. turned power back on, everything was good. towers worked for a couple weeks. the other day one side of the tower stopped working. in the past, i had had some trouble with the exile ZLD. i thought it was that again. i did not look into it more. this morning we started out for a dawn patrol without any towers. looked at the amp, it was in protect mode. tired the power off, but that did not work.

what and how should i look for my problem that is causing the amp to go to protect mode? what other info do you need? the amp is exile 4 channel i think. tower speakers are 2 XM9.

thank you!