Brown Spots in Abalone Mushroom and bacterial spots in Oyster Family mushrooms are caused by Pseudomonas fluorescens bacteria. The primary symptom shows up in Abalone Mushrooms as light yellow mushrooms emerging from the bottle’s opening in a curling condition. Mushrooms will be flawed, undeveloped and not fully bloomed. Groups of 2-4 mushrooms start to grow with clusters of undeveloped stalks. There are light brown spots scattered on top and under the caps and stalks. These spots will get darker in 1-2 days and the spotted areas will be flattened. The symptoms in Oyster and Phoenix Oyster mushrooms show up as yellow mushrooms emerging from the opening of the bottle. The mushrooms are smaller than the usual size and some are curling. The mushroom clusters are undeveloped, withered and yellow. This yellow and withered condition is different from an insufficient dampness condition. If the next newborn mushrooms are still yellow and withered, then it was caused by bacteria. If there are a lot of bacteria, all the production will be damaged.