Colours Fading
 

In the last week, I've noticed that several of my corals have lost their vibrancy.

-The kenya trees are now white instead of purple
-My neon green candycanes are now yellow
-The brain's flesh is going from green to white in one spot
-Green zoas are becoming lime

What's happening? Do my lights need changing? Could I be oversaturating the water conditioner?

Could be lights, but that would take a long time. Generally it's water parameters, check nitrates/phosphates see if there's any issues, or if you're getting excess algae. Could also be biological since you have softies and LPS, are you running carbon? There's many different things it could be.

I just put carbon in, but that was after the colours deteriorated.

Chemical warfare?
 

With your small tank, and corals like leathers/toadstools, there may now be chemicals emitted by the new corals.

Msjboy