Users behind 1 IP not load balancing across pool members

I would recommend that you try adding a OneConnect (/32 mask) profile to the virtual server. This will instruct the BIG-IP to load balance and perform content switching on every HTTP request instead of once per TCP connection. This is an issue that I usually see when you have a proxy / CDN in front of the F5 BIG-IP which translates many client source IPs to a single proxy IP.

create ltm profile one-connect ONECONNECT-32 defaults-from oneconnect source-mask 255.255.255.255

modify ltm virtual <VS NAME> profiles add { ONECONNECT-32 }

Let me know if this helps.