It could be either. Older hot tubs used silicon to seal the jet fixtures to the shell, that could be the source of your leak. However, sometimes it's the connection. Many tubs use glued fittings, the leak could be there or the line developed a pin hole leak.
Unfortunately, you need to actually look for the source of the leak. If it's not a full foam insulated tub, an inspection camera may help if it's in a hard to see location. There are ones that plug into a cell phone that are not expensive or you can get a dedicated camera from Harbor Freight for about $60. The dedicated camera has a better camera and it's a semi rigid wand which can be an advantage in this type of situation.
