Small Coolant leak from????

So I think I have a coolant leak, only I can't tell where. The only reason I know it's leaking is because the overflow bottle level is going down, but this is slow over a very long (more than a year) time. What would my engine look like with dried coolant? The water pump and thermostat along with all the coolant hoses and radiator where replaced about three years ago. The truck never overheats and the radiator itself has a full tank of coolant.

Should I get it flushed and refilled? Put some stop-leak product in it? Other suggestions?

 

My coolant level in the reservoir goes down very slowly over time too...never thought anything of it.

 

Mine did that for awhile, didint find the leak until I did my timing belt change. Turns out my water pump had been slowly leaking for a long time by the amount of crud that I had to dig off the front of my engine and from around my pulleys. So might want to re check that as a suggestion. Oh and FYI I never smelled antifreeze for some reason, go figure.