Brake, ABS, and skid lights all came on

You or a shop need to find the leak

 

How much lower is "much lower"? I'm seeing a lot of posts going with the thought that there must be an external leak, probably all because of this sentence. But the fluid level does normally look different depending on whether the system is zeroed down or not at the time that you check, and sometimes people don't take that into account.

 

There are two different types of leaks when it comes to a 3rd gen Prius, external and internal. External is generally easy to find by virtual of a wet spot in the vicinity of the leak. The second, less obvious kind is internal where the booster system leaks pressure inside the sealed system. The fluid level in the reservoir doesn’t go down but the electric pump can be heard running more and more frequently and for longer and longer periods of time. This is the more expensive kind to fix. It can be a DIY proposition but that requires investment in a decent OBD2 reader compatible with hybrids and capable of two-way communication for the bleeding process.

 

Head Gasket, Water Pump and Inverter next.