sigelnz: ... my other Airport Express boxes are working as repeaters via the Airport Extreme
Repeating wifi usually puts some serious hits on performance of the wifi (anecdotally I've heard as much as 70% real world drop). Seeing as you just got Fibre put in you may be creating a slowpoint within your own network by doing this. It would be worth testing. Run a speed test, then turn off all the repeating and run it again.
If I was setting up the gear you've described (a Huawei router, airport extreme and a few airport express APs) this is what I would do:
Put each of the airport devices wired direct to patch panel, or to switches within your own network. Keep the settings the same on each of the wifi APs EXCEPT the channel which you change to a non-overlapping one (1-6-11).