We have a log home in the UP of Michigan. It is 25 years old. Until 2 years ago, we sealed it with CWF oil, and re-did it every 3 years. We would power washit, then apply the sealer. It always looked like new. Two years ago, we applied Penofin, and it looked beautiful for about 9 months. After that it started turning black.gets darker and darker.Called Penofin and was told to use 50 50 bleach and water. Did nothing. Now we just want to get rid of it.and put something on it that won’t turn black