Common on the 04-06 rx330 that the radiator leaks from the side seams of the base, pop the hood, look inside from the top towards the inside of the radiator.
Replace timing belt along with water pump serpentine belt thermostat at the same time, camshaft and crankshaft seals replacement at the same time isn't a bad idea.

Your car uses toyota pink coolant - which is already premixed, so don't freaking add any water to it like some one suggested.

 

States in big letters on the front label that it is pre-diluted and not to add water.

http://lexus.sewellparts.com/accesso...2006/4371.html

 

Checked all around yesterday - nothing. Might have been my paranoia. Coolant is in place and doesn't move anymore.

And yes, it is diluted Says right on it

I'm always saying that I might be stupid, but not that much.