I have a 17 year old Pro-Ject Debut SE which I hooked up to a pair of Fives plus a Sub last year. I was very happy with the sound but recently I've made some upgrades to the turntable. Main one being a much better cartridge - the Ortofon MM Blue. It sounds so much better and really makes the Fives and Sub shine. So well worth doing if you love your vinyl. It easily sounds on a par with hi-res streaming now.
I notice that you flipped the FIVE’s to vertical orientation. Is this better sounding?
Yes and I also changed the RCA cables plus the sub platter and turntable mat (as well as the cartridge). Next to no hum at all now. So much better 
Experiment with pulling the speakers forward to the cabinet edge. In addition to some subtle sonic detail changes, this might impact the hum. Also, experiment with RCA cable positioning and keep them bundled away from the electronics as much as possible.
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