Raspberry peanut butter mead, this happened after racking into tertiary. Primary and secondary had raspberries freefloating in the container, so it miiiight just be floating bits of raspberry. When I shake it up, they briefly sink and float back up.
Funny thing is, apparently, yeast can metabolize fat - according to Dr. White, they can use available fat instead of synthesizing their own using oxygen on growth stage to build new cell walls. It's not a lot of fat they need though, but quite measurable amount, and only on exponential growth.