On average I have 80-100 Guineas, year round... free rangers lose toenails, penned flocks lose toenails. Depending on what they can get into/hung up on. It's common. A lot of Guineas are prone to growing extra long toenails, which makes them even more prone to catching them on something and ripping them off. Check your coop, pens, roosts etc to see if there's anywhere/anything obvious that the bird may have caught it's nails on and ripped them off. Usually if the flock is going to cannibalize a bird it goes way beyond just toenails, but if blood was on both of those nails the rest of the flock could have been attracted to it, and pecked at them.
Guineas need a higher protein diet than typical back yard poultry flocks do. I have never heard of or seen a case of gout in a Guinea caused by the diet. Gout is a lot more obvious than a couple of ripped off toenails... can you post a link to that article?
Posting pics of your bird's feet may get you better help/advice too.