My fish get fed these crisps and go mental for them. It's a struggle getting them to eat normal flakes now.
I don't believe for a second that the food killed your fish. More likely your cleaner saw a wasp on your air pump and doused it in insect spray, or someone coated themselves in hairspray with the lid open, or decided Mr Muscle was the best thing to make the tank shiny.
Even if it did happen, I would have been complaining to the manufacturer at the time and having a proper investigation, not having a half hearted swipe at them on an internet forum a year down the line.
Ps. I don't like the photo in your profile, that's not responsible fishkeeping in my book.