Just to update, I have been doing abit of reading of the archives forums as well as other resources. It seems that it recommended again blowing too hard for the yamaha, especially new ones with unseasoned reeds. In addition, using the tongue contributes additional saliva into the melodica (from a harmonica forum). I am guessing that a suggested fix would be the to increase the gap between the reeds?
To provide some context, I am actually a brass player and I do blow pretty hard into my melodica as though it was a brass instrument. We tend to use our tongues to “tongue” and articulate notes. I tongue alot as practice. I did notice that the gap between one of the affected reed was totally soaked underneath when I had open it up with just 5 minutes of playing. The gaps between all the other notes seemed generally equally spaced with the except of the high F did seemed wider and sounded abit off.
Sorry for the long posts!