Quince apple tree disease
Hi- we don't think this is a disease. (Interesting that your other trees seem unaffected.) It appears that mostly older leaves are affected on this particular tree. New growth looks more normal. It's possible that the leaf discoloration and browning of leaf edges was caused by some environmental stressors such as extreme weather, soil conditions (too much or too little water, incorrect soil pH), or a damaged or compromised root system. Pesticide applications can also cause leaf burn.
There is nothing to be done but remove dead and dying leaves, keep the tree well-watered during hot, dry periods, and take a soil sample from around the affected tree and have it tested:
Thanks so much.
You are welcome.