Bad Cornwall IV?

First guess is a tweeter is blown.

Use the "Ear" test to verify.

Being a Forte 4 owner, I would disconnect speakers from the amp then remove the binding post module from the back of the speaker. Next, make sure red wires are connected to red posts and blacks are going to blacks. Check for solid connections.

Finally, I’ve researched Anthem receivers and read that they have problems with their room correction software and user interfaces as well. These problems may have been worked out by now, but this is what I read.

If possible, try to disable room correction and play as close to "straight two channel audio" as possible. See if this changes anything.

BTW, are you using single or bi-wire connection?

Those slate colored things, on the outside of the binding posts, are called "jumpers" they allow you to use a single speaker wire to feed your speaker. When you remove the jumpers, you can use two speaker wires (bi-wire) which people say sounds better.

Note: the binding posts, at least on my Forte 4s, do not allow extreme tightening with spade terminals. You must use banana plugs or your contact is compromised.

Glad to hear you solved your problem!