Try using Feliway. It is a synthetic facial hormone that causes cats
to be more content. It works most of the time.
You might also want to have a vet give them checkups. The cause could
be organic.
Also, has anything changed in the environment?

It's the food. You ran out of their favorite food then went to a crap food
backup plan. Now they know their food supply can be altered, or should I say
threatened. Hmm, something they never experienced prior. You elevated their
inner instincts to a more serious degree. The tension and concern over the
superior food supply is greater. Ditch the good Iams pouched food
altogether, for quite some time. Stick with the less desired food and the
concern over it will also become less. Canned food and dry food isn't so bad
anyway . The tension will probably go away. I know from experience, with
multiple cats, tampering with the food can create hostilities amongst them.
Stability is key. Problems are usually corrected when a food is available
they are not crazy about. They eat it because it's there, not because they
like it.