Forgive me if you know the following …

Setting parts of your system to what appears to be the same clock may not be enough.

Two clocks called 44.1 will be just that – 2 clocks running at a similar but not identical speed – clicks galore !!. 

You have decide on a master clock source and synchronize everything else to it.

One approach would be to make the H8000 the master, and synchronize your RME boxes to it.

You could use ADAT as the sync signal. Connect one of these from the H8000 to the RMEs, and set RME "Clock Mode" to "Autosync", and then set RME "Pref Sync Ref" to ADAT.

 Alternatively, select one of the RMEs as master, and slave the other one and the H8000 to it in a similar way.