I think commercial systems use 5/16, not 5/8. 5/8ths is a good commercial-grade watering hose. You can jam 1/4 on a 5/16ths fitting by heating the hose in boiling water.
Have you checked the fit for the kegs?
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk