Can't imagine any other cause other than bad fuel... Water or algae.
I had 2 episodes of bad fuel a while back, one of which was totally my fault. Even before that I was sick of the in series low capacity fuel filters. Once you get squared away fuel wise, I highly recommend replacing the first in line filter with a large canister type. I used a Cat 1r-0750 2 micron filter with a Napa 4770 head, mounted sideways on the frame.