Water cooling maintenance

What would you be trying to do by tightening them further? If they're solid and not leaking, then they're solid and not leaking. Tightening them will only stress the components and the tubing.

Actually, unscrew them and see if the tubing has slipped off the barb at all.
But yea, as long as the compression's are finger tight, they'l be fine.

If you have leak tested and not had any problems, making any adjustments to the tubing or fittings will only mean you need to leak test once again to ensure you didn't cause any problems. If you've installed all your gear, leak tested and there aren't any problems, you shouldn't need to adjust anything unless you spot a problem. This is why careful attention to detail during install can help you down the road.