Hi! I had my oak worktops stained a lovely dark colour and oiled about 2 years ago. They were showing signs of wear, so I re stained and then re oiled. The worktops are now patchy and in some places are a little 'ashy. I also can't wipe them down with a damp cloth without the stain coming off! Help! What have I done wrong!! I used the same stain and tung oil that my builder left here (so a couple of years old) could that be the problem?