i got a brand new fender 63 avri and i really like the strings on it. In fact, i bought the same fender medium gauge strings to replace the old ones. However, after only six weeks, the are starting to feel thick and slowing me down the way strings start to feel when i need to replace them. I play fast metal and need fresh strings to be able to play my parts but usually they last about three months. Is there some reason why these might be getting dull after six weeks?