Code P0420 bank 1 and bank 2

SES has been on since vehicle was purchased 2 months ago, but have had no driveability concerns until now. When cars MPG is decreasing and car has begun jerking/jumping at idle in all gears as well as during acceleration. Went and had codes read, P0420 on Bank 1 and Bank 2, so confident that catalytic converters are not the issue since getting struck by lightning is more likely than both going bad at once. Checked air filter and intake for obstructions, debris, and leaks and found none. Any suggestions of where to start or what to check/try?