Possible Leak at Plumbing Solder Joint
If there was water in the supply line when you went to sweat the joints the water turns to steam and can cause very tiny leaks like you have. I was taught to get as much of the water out that I could then pack some white bread (no crust) tight in the pipe. The bread makes a plug that once soldered a flow of water will dissolve (just need to remove the aerator) I do this on pipes that have been damaged and need a new coupling on both sides works great and no leaks, I believe this is the problem because the hot should never have condensation and if the water is not running the cold should not be much different than the room temp.