Ok, So not a Rocket5AC-Prism? It's the Rock5AC-Lite, -ptp or -ptmp. (ubnt blundered the Prism name in reguards to the tech and what it's it and how. They should have said Half Prism and Full Prism.)
If you really plan to replace 90's with three 30's you need to be looking at the v2 or v1 R5AC-Prism with GPS sync.
I'm in a very noisy area and I have had the same issue with the horns. So like I said, aim it up higher or down a lot more. Remember that the 90 deg. sectors have higher gain and a 6 deg. vertical beamwidth.