What aux emitters are you using? I got some purple emitters, but they are almost UV (very dim). Instead, I've had to use pink emitters to get anything close to a visible purple.
I think these are the same 0603 purple LEDs that you might be using. They are very close to UV but I haven't had any trouble driving them from the stock driver, and they are only super dim on the low mode
To be fair, I was trying to use them in an illuminated switch, and they could barely be seen through the translucent silicone Convoy button. Maybe I need to give them another try as aux emitters.
When they are not lit, do they look clear or orange/yellow? I have some near-UV ones as well, they have very high Vf and look clear, while my pink and purple ones look orange/yellow when they are not lit.