Sorry to cause confusion. I will explain in more detail what "unplugged input from channel 3 and plugged it into channel 2. Hiss is gone from channel 2 and moved to channel 3 (not the mixer channel)." means.
On the mixer I swapped the wires for channel 2 and 3. The hiss moved to channel 3 and there was no hiss on channel 2. That tells me that there is nothing wrong with channel 2 on the mixer. I have heard of some mixers having channels go "bad" and creating noise so I was confirming that. Now to go over a few of the replies...
I call a channel each input into the mixer.
I have the same EQ settings for channel 1 and 2 (both guitar inputs) and hiss only shows on channel 2.
Now put everything back.
The hiss is back on Ch 2
Now reverse Ch 1 and Ch 2 at the mixer. does the hiss move?
Now reverse ch1 and ch 2 at the platform does the hiss move?
If it doesn't at the mixer and does when switched at the platform, it is a ch on your installed wire.
I did reverse Ch 1 and Ch 2 at the mixer - the hiss did not move.
I also reversed ch1 and ch2 at the platform and can't remember if it moved. I seem to think it didn't and that was why I started trying to confirm that the mixer was good by plugging a mic into the mixer ch2 which made the hiss go away.
One other thing I just tried was I disconnected the Digitech pedal and the hiss left from Ch2. So...I'm guessing there must be something wrong with the pedal's XLR outputs. Thanks for the help, and sorry for the confusion in my original post.