I recently planted Liberty in the remnants of an old sand box. It was very sandy. I didn't really think twice about it since I have 4 other hostas within a 3 foot radius of it. I'm only now reconsidering it after a few days of thought. Do I have a legitimate concern or are they unfounded?
Since you just planted them it is not late to pull them out, amend the soil and then plant your hostas.
my concern with just sand is they might not do well but someone might have a different idea on this.