There are posts on Bobo on both the perennials forum and the Hydrangea forum here on Houzz and gardenweb.

I don’t grow these, but the ones I have seen planted in gardens here in NH have done well. They have been in soil that drains well.

Yeah I searched through as many threads about Bobos I could find. I did see one similar issue, however most threads are singing the praises of Bobo:) I'm convinced they are a little more sensitive to wet feet than other panicles. The bed is completely enclosed....bordered by the house and sidewalk. I could build it up slightly...maybe 3-4" and slope it back down to the sidewalk. Would it best to do this with good topsoil or something looser, like compost?

I honestly don’t know how best to do that, though whatever you use should have similar texture to the soil there. If mounded too much you may find that soil washes out onto the sidewalk. If you decide to build it up in some way, be sure to lift the Bobos as well. Don’t mix whatever you use into the soil as soil texture changes can lead to issues with the way water moves through the soil, either puddling around the base of planting holes or staying perched where texture changes.