The second ball valves may just need snugged a little ... that usually stops a leak from that location.The third looks like the joint below the valve is where the leak is/was.The first may just be the bleeder ... you may be able to snug it as well, but with that corrosion, I'm not sure.Those valves should have been checked shortly after installation (a few weeks) and then periodically as part of your annual, pre-heating season maintenance.

I showed him the dust & corrosion on the window Al capping & he was still not convinced.