check the twisted val is not buried, it likes to sit with only it's actual roots in the gravel so if there are any green bits covered up, just wiggle it out a bit so you can see the roots. Any green bits that are in the gravel will wither off and die. If the roots are not big enough to weigh the plant down you could put a stone over the top of the root.
I don't think dwarf sag objects to being planted right into the gravel.