Mazus reptans died for me, too, even after making a good sized clump. And I killed a couple of Corsican Mints until I decided putting some rocks next to them to retain some soil moisture might keep them from drying out so fast. It did work, and then I saw it self seeding in my lava rock path, I guess it really liked the rock microclimate. So maybe your plants will like the sand, or maybe not. Let us know how it turns out.

I googled the Hutchinsia and the photos are all in rocks, it must be another one that likes rocks. Maybe you could put a few rocks around too. The last couple of expensive rock garden cute blooming plants I bought croaked in short order.

LOL..................I have rocks, & more rocks, and rocks galore here...............my landlord told me to eliminate the stones/rocks that surrounded/delineated the beds. Plus.... some driftwood pieces people would kill for!
Now then...........I have 35 Hutchinsia planted and I'm confident the landlord would have a heart attack with the idea. I will however hope for the best; if they grow in rocks maybe sand won't decimate them; the ants will be ecstatic with the foundation material tho. Thanks TONS for your response, & time for me Hemnancy. Enjoy the rest of the weekend. I have a glass of wine in hand, after working with a computer tech for the last 1hr. 45min. He was however a peach, patient, and not foreign in language.
Good Nite, Jaemy