While I was under the hood...

Just finished messing around under the hood, washing cleaning, and so on. I noticed that the new radiator, a nissens, that I installed last September, was seeping coolant around the upper tank. It looks as if the seal to the radiator body is defective. I was interested so I jacked the car up and you guessed it, the lower was seeping in the same manner. Now, it's not gushing or anything. It's just enough to annoy me. The resovior is only about a finger's width below the full line. Right where it was when I serviced it in September. So I konw that it doesn't leak that much. I was wondering if anyone else has experienced this. It's staying in for now. It cools well and I haven't had any other problems.