Toyota A/C -finding a leak question.?

The dye will glow until you clean it off, so no, it doesn't need to be leaking at the moment you have the light on it. I would take your light and look at the compressor next, then the hoses on top of the motor. These are the most likely failures; rocks hitting the condenser, seals in the compressor (the only component with moving parts), or hoses getting rubbed or brittle from heat.