I would have guessed spokes too. Nothing terrible, just them stretching under a little strain and becoming looser. Just go get the wheel trued and all will probably be fine.
@Velocio started
London Fixed Gear and Single-Speed is a community of predominantly fixed gear and single-speed cyclists in and around London, UK.
This site is supported almost exclusively by donations. Please consider donating a small amount regularly.
I would have guessed spokes too. Nothing terrible, just them stretching under a little strain and becoming looser. Just go get the wheel trued and all will probably be fine.