Decaying, rotten.

That moulders; decaying, crumbling, rotting.

That dissolves, in various senses: see the verb. intransitive.

Biology. Melting away in the process of growth or of decay (cf. deliquesce, v. 1b); having a tendency to melt or become liquid. Also (occasionally)…

Crumbling; friable; (of a fire) smouldering. Also figurative.

That decomposes; usually intransitive undergoing decomposition, in process of organic decay.

That disintegrates (intransitive); breaking up, going to pieces.

That crumbles, rots, or decays.