Yes, another. My coworker. Her BLUE bettafish, she had gotten 3 weeks ago at the store. She had him in a 5 gallon, heated and filtered, cleaned once a week, gravel cleaned well. She added tap water conditioner ONLY, never used harmful cleaners, and fed him twice a day, about 6-8 pellets (shaker type). She noticed him going grey on the fins - when she told me I thought "oh hey fin rot" but the description of the "ash grey on his fins, which 3 days later fell apart and he died after it spread" matched perfectly my Maine's sickness.
The male was about the same age as Maine.. A few months younger, actually. About the same shade of pretty blue. She thought it was the cats fault, or that she wasn't taking care of him well enough - but I asked all the good questions, and she did perfectly for caring for her little guy! She felt really sad for her little guy... He lasted 3 days with this sickness - same as my boy (I put mine down, hers passed away). She felt very distraught - thinking she killed her fishy. So I told her of my fish, and connected it to how her fish was.
I definitely think there is a bad bad bad blue genetic gene floating around where I live! two in less than 2 months? No way. To make it worse, I got a "black male with silver fins" and he ended up being BLUE with red, silver, black and blue in his fins. So I have him heavily watched right now... If he came from the same breeder, the breeder could be unknowingly breeding the gene!