We recently stripped the stair treads and they look beautiful, however there was a lot of caulk/paint where the tread meets the riser.Now there is a gap between them.We can not get behind the staircase and can't think of anything to fill the spaces with that won't show and look terrible.I'm not sure how we failed to anticipate that this could have been a problem.Does anyone have any ideas on how to solve this?

Thanks