Why is my beergas gone already!!

I recently bought a stout faucet beer gas cylinder and regulator. The first time i hook it up to one of my stouts everything seems fine till the next day when i go to pour a beer and nothing comes out. the tank was empty!

So i thought it was my connections, even though the only connections are the regulator to the tank, the hose to the reg and the hose to the QD. I refilled my tank and used a spray bottle of star san to see if there was any leaks after i really tightened the connections and nothing was leaking.

Would a whole 5# tank of beer gas leak out overnight with a significant leak that would be easily detectable? the only connection that hasnt been used before with just my CO2 bottle is the connection at the bottle and regulator, i have used all of my hoses and disconnects with my Co2 with no problems in the past. Also its not the keg leaking because i have used multiple kegs and both the kegs have been used with co2 with no leaks. could it be a faulty regulator maybe? any ideas of what the problem could be? i am already out about 70 $$ in beer gas and cant really afford this to happen again. thanks everyone!

Just because the kegs held pressure before doesn't mean they are
sealed up good this time. I'd check to make sure it leaking out of the keg.

kegs hold pressure fine, they are not leaking at all right now

Are you using Teflon tape on the regulator?

At work the Argon and Nitrogen cylinders I use tend to have very slight leaks unless the male fittings are properly taped up and cinched down tightly. THe soapy water test works well, but sometimes it takes a few minutes of staring at the bubbles to make sure no new ones are forming.