Wetsounds help?!

I have 2 Rev 10s running off a Syn 4 amp with a WS420SQ feeding the amp. This weekend I lost all base in my Rev 10s (highs still play). All my in boat speakers and sub still have bass but they are powered by a different amp. I have checked all settings on 420SQ and amp and there are not any problems. I also switched outputs on the 420SQ and confirmed that the problem is not in the 420SQ. So based on that I have to assume the problem is in the amp itself because I think the chances of both speakers losing bass at the same time is very slim. Short of rewiring the tower speakers to another amp to confirm the problem is with the amp, is there anything else I can do? And do amps typically lose just part of a frequency? I have checked all gains, crossovers, etc and don't see any problems. And I didn't change anything prior to this happening. Appreciate any help anyone can offer.