If you squirt a bit of Dawn into a cup, add a bit of hot water and use a paint brush that you agitate it with up and down to make bubbles, you can dip the bubbles onto ALL the fittings- including the ones built into the hoses.
I've found more than one hose fitting leaking over the years...and orings in the connector.
Don't forget to check the BACK of the connectors, too. Sometimes the leak can come out the back of the big black nut, not just the front.
If you find a leak on the crimped fitting into the hose (most I've seen are crimped), replace the hose. Make sure you use a thread sealant and it's pretty simple and inexpensive.
Usually box stores like Home Depot, Tractor Supply, Ace Hardware, etc stock them. Might even find a sale now that we're getting towards the end of grilling season ;)