I left 4 large turbo's in my tank for several days after they apparently died (back when I had a wicked temperature spike, in the first few weeks of cycling).
Finally pulled them out, and nearly spontaneously vomited from the smell.
If you think they're dead, and nothing's eating them, I'd remove them. Anything that smells that bad has got to be contributing a lot of water to the water.
180G build thread
180G All-glass with dual megaflows in a custom stand
AquaC EV-180 skimmer
250 pounds LR
160 pounds aragonite
Custom acrylic sump from GlassCages.com
2xPCX-40 return pumps
2x250MH 14K, 2x175MH 14K - PFO lighting, 2x65W PC
No-name 36W UV
Water General 125GPH RO/DI