Whatever it is, I've got the same thing on my two quinces. Earlier in the year I pruned out branch tips that had obvious fireblight (black, limp). Then I pruned out all the branches that had cedar-quince rust. If this disease requires pruning I may never see fruit on these trees/bushes.

I believe this leaf browning is caused by fireblight. Fireblight has many different appearance modes and this is one of them. The reason why I am fairly certain that this is fireblight is it always shows up along with fireblight strikes of the more standard shepherds crook. I should probably be pulling these off but they don't look infectious to me so I usually just leave them.

Scott