Controllerless Networks

I am very new to Aruba IAPs and generally less-than-expert about networking as a whole, and am having some trouble for which I hope you all can help. I have 2 IAP-315s to connect to my network. Router is set up with 4 VLANs, 10 management, 20 VPN, 30 open internet, 40 guest.

My desire is to have 3 SSIDs on the IAPs, one for each VLAN - 20, 30, and 40. My attempt has been to plug the IAP into a switch port trunked with 10 untagged, 20, 30, 40 tagged and then send the traffic from each SSID tagged for the specific VLAN. This all works great with one AP. AP is assigned and IP in the management VLAN, I set up 3 SSIDs each with a statically assigned VLAN tag, and when I log into each respective SSID it assigns an IP in the proper port range for the VLAN and applies all the expected router and firewall configurations. 

My problem is when I attempt to connect a 2nd IAP. I plug it into another port on my switch trunked the same way: 10 untagged, 20, 30, and 40 tagged. It is assigned an IP within the management VLAN, but instead of being seen by the virtual controller, the original IAP becomes inaccessible to the webUI (though the networks still function). Eventually the 2nd IAP comes online but does not see the first at all.

The other strange thing is that if I simply plug both IAPs into a port on the switch with VLAN 20 untagged everything works fine. They are assigned an IP within the VLAN 20 range and they see each other and mesh as they are designed. But now they are constrained to VLAN 20, and I want them to be able to offer an SSID for each of the 3 VLANs.

I'm sure I'm missing something, probably simple, due to my general ignorance. I hope I've been clear about my problem. Any help would be most appreciated.