Quick connect fittings leaking

[rob in ore]

The fittings that supply the backhoe (Woods BH77, dealer installed about 8 years ago), have started to leak a little more than I'm comfortable with. The leak is most noticeable when the backhoe is removed and the supply/return lines are plugged into each other. These hoses and fittings are only used for the backhoe. They are only connected/reconnected three or four times a year.

Could the fittings be worn out with such light usage? Is there something else I should look for? The hoses and threaded connections are dry.
Can I just change the fittings on the tractor or should I change the mating set on the backhoe at the same time?

 

[5030]

Internal O rings need replaced.

 

[WranglerX]

I had a leaking fitting and a 59¢ "O" ring from local auto parts fixed it.... Might be able to get a bag of 8 or 10 at TSC for $3.95

https://www.tractorsupply.com/tsc/search/o%20rings?

 

[rob in ore]

The real culprit turned out to be one of the crimped connections. I guess they weren't as dry as I thought.
I replaced the o-ring. Thank you for that, I didn't know there was such a thing in there.
When the leaked returned, I wiped it all down again and was able to see it while working the control lever. A new hose and it's fixed.