Please try using the command line option -mi with different values (for example 8, or 9 instead of the default value of 10). You can change it only for the RX560s by using it like this:
-mi 8,8,10,10,10
In the above example the first two cards will run with mining intensity 8, and the other three - with mining intensity 10. This assumes that the RX560s are the first and the second card and you have five cards in the rig. The order of the cards must be the same that is listed by PhoenixMiner when starting up.
Didn't change much, still dropping hashrate.