Q.Dark Spots Appear On Established Leaves, Top And Underside Of 4 Year Old Baytree.
New leaf growth appears unaffected but is decimated once established. I have noticed minute spiders / mites and wondered if this was the cause. I would be very grateful to receive advice on identifying and treating the problem. Thank you.

Certified GKH Gardening Expert
It could be psyllid damage. I also included information on other causes of leaf spots. These articles should help:
https://www.gardeningknowhow.com/edible/herbs/bay/dealing-with-pests-on-bay-trees.htm
https://ipm.ucanr.edu/PMG/PESTNOTES/pn7423.html
https://www.gardeningknowhow.com/edible/herbs/bay/sweet-bay-leaf-spots.htm
https://www.gardeningknowhow.com/edible/herbs/bay/sweet-bay-leaf-tree.htm
Also make sure the plants are not overfertilized. Excess minerals can cause dieback on leaf tips.