Possible Leak at Plumbing Solder Joint

I am currently renovating my bathroom and recently removed the copper supply piping back to and including the hot and cold shutoff valves to repipe for a new shower valve. Everything was repiped with copper, cleaned, prepped and soldered including 2 new ball valves, a new shower valve and 2 new drop ears for shower and tub. I turned the water on and everything seemed to be good and none of my joints were leaking. I returned to double check the pipes the following day (about 10 hours later with pressure on all joints overnight) and there were no leaks, but I noticed on the "house side" of both shutoff valves there is the slightest amount of moisture on the surface of the solder joint between the shutoff valve and copper pipe. No dripping, not enough moisture to run down the pipe, just barely enough that when I run my hand across the joint I can feel and see the slight presence of moisture. It almost feels like condensation but I don't even want to call it that because the amount is so minimal. Is this a problem? Possibly usual for a new joints like this? This occurrence is happening on both valves and visually the joints look good so I don't believe it is a bad solder joint. Any help would be appreciated. I want to make sure everything is good before I install cement board and tile.