I lost the luteus. It lasted 6 months or so. In retrospect, this should have been expected. Just a week or less ago it was still sucking in several accidental pellets and blowing them out of its gills. It was my wishful thinking that he doesn't blow all of them out and actually partakes of some. But now I think it just never fed, no matter what I tried - pellets, fish, veggies.
Wes offered perhaps one of the few possible causes that the pleco had a parasite or a worm, that could have been purged with praziquantel. I usually administer prazi via feed. In retrospect, I perhaps should have tried giving it prazi baths.
Other keepers of this fish report no problems whatsoever with feeding their luteus, regardless of tank mates, hiding places, diet offered, etc.
Some photos of my sad guy: