I don't see any moral conflict and I'm real big on doing the right thing always.
The other guy's work didn't pass. If they want to hire you to fix it, it will cost them. And it should. If it's a fair $1K to rework the chandelier, you've got to charge them the $1K or consider it charity. I'm all for charitable work but rarely do customers with chandeliers in 10K sq ft homes need a hand out.
You're not "cracking them over the head" with an extra. You're charging them extra for extra work. If it wasn't in your original agreement, they're scamming you if they expect you to fix someone else's screw up and not charge them.
