I lifted the hood and saw that the brake fluid was very low. Quick troubleshooting revealed a leak at the slave cylinder.
Did you mean to say at the "slave cylinder" or at the "brake master cylinder"? Even if the clutch circuit lost all of its fluid, it shouldn't impact the brakes, as the reservoir outlet for the clutch is higher than the ones for the brake.
I found mine is leaking where the pipe from the reservoir goes into the clutch master - it seems the seal there cannot be purchased separately - I only just rebuilt the cylinder and must have damaged the seal putting it back together - anyone else had this or got a tip to stop it leaking?