"Merlin" wrote in message

The boron thought is an interesting one - as you say, can't do any
harm
to provide a few extra nutrients anyway to eliminate the possiblity.

Be very wary about boron amendent - too easyt o overdo it. And, if it
was a boron deficiency, you should have noticed problems with the
leaves, and no spotting of the skin before you got the core of the
Quince being affected. You didn't mention leaf probs so I don't think
it would be boron deficiency.