I brewed a dry Irish stout (~5%abv) awhile ago, bottled 3 gallons, and then split the remaining 2 gallons into 2 separate 1 gallon carboys to age with 1/2lb of frozen cherries I bought from whole foods. The initial bottles were really good, but I recently checked on my aging remainder and found that one of the gallons has a white film at the top, and the other does not. I am normally pretty meticulous about cleaning and sanitizing equipment. I have done some searching and it seems to likely be some lactobacillus infection, but I am still a little concerned. Does anyone have any experience or suggestions relating to this?