Hi, I've been playing for almost 10 years. I practice everyday for about 30mins to 1 hour. I was able to play alternate picking at some medium tempo but there used to so much string noises (hitting extra strings while switching), so I changed my picking grip and position. If I were to play on a single string, I can play up to a speed of 150BPM but when I play on multiple strings using alternate picking technique, my picking speed reduces to about 100BPM. Can anyone help me with this? What could be my problem.