Orbi RBK50 & RBS50 iPad vs Mac differential thru-put

We have a three unit Orbi setup (router + 2 satellites).  Bandwidth thruput (c. 70mbs) is consistent at all points in our apartment (2200 sq ft) when measured on iPads.  However, thruput on (two) Mac desktops (running 10.13.1 and 10.12.3) is variable and poor (10-20 mbs), and sometimes nil.  Desktops are located near a satellite.  Desktops register full bandwidth when moved to same room as base router.   Can only conclude that there is some sort of conflict between the Macs and the satellite.  Would appreciate any guidance re how to resolve!   Thank you.