Buying Emerse Anubias

[AmazonPassion]

I've bought emerse Anubias a couple of times in the past and usually some Anubias ends up dying. I don't bury the rhizomes into the substrate, I just cram it into the nooks and crannies of the driftwood or tie it down. What happens is the leaves and stems just float away and the rhizomes turns into mush.

Any ideas why this is happening?