Multiple AP on Single Routerboard with Hotspot

Not sure if this belongs under “Wireless” Support..

I have a working Access Point (wireless - wlan1) with Hotspot, running on RB500 (MT v3.16).

I have now added a second AP (wireless - wlan2) onto the same routerboard.

eth1: 192.168.1.1 (this is also the default gateway)
wlan1: 192.168.10.1
wlan2: 192.168.11.1

Additional config done:-
-Created two hotspot servers, with each configured to a specific wlan interface
-Created two server profiles for each server profile
-Created a static route to each AP subnet (although a dynamic route was created by MT)

Results:-
Both AP’s work correctly and users can authenticate, and access the default g/w..internet
From the routerboard, I can ping any host connecting to the AP’s

Problem:-
Users from both AP’s cannot ping each other


Any suggestions as to why subnets cannot see each other?
(Routing, firewall/nat rule?)

Thanks