Hi there. Thanks for your question.
At the outset, I would like to compliment you for stopping alcohol and staying dry. Based on the description that you have provided, in the background of chronic Alcohol use, one of the possibilities for dark patches is low levels of Vitamin K. This can happen as a result of Alcohol related problems to the liver
I suggest that you see a physician (or your GP) and get yourself tested including your liver function tests.
Hope that was helpful.