Huh? Where else are they used?

You mean third party apps like block explorers etc?

The actual four individual bytes are defined only once in the entire code.

Change them there and all parts of the code using them use the new values.

You did not answer the question about whether you copied one other coin's unique magic bytes or copied the same ones it had already not made unique, so that maybe you and who-ever you copied from both are going to run into this collision of networks problem.

From where did you copy them? Had they made theirs unique?

-MarkM-