Do they have layer-2 connectivity? I've done somethinig like this to myself where 3 iAPs formed one VC in VLAN5 and 7 iAPs formed a second VC in VLAN4.
I solved it by shutting power off for the 3, changing their vlan assignments and restoring power.
Once they could "see" the broadcasts, they joined and all has been well since.
--Matthew