Q.Orange & lemon tree leaf drop
Help! Until a few weeks ago we had a healthy lemon tree and orange tree in our greenhouse. No idea what has happened. Can’t find anything like it on the web that looks like this disaster zone. Started to lose the odd leaf and suddenly we have the equivalent of tree alopecia. Can you help please?
Thanks
Colin

The most common reason for leaf drop on Citrus is uneven watering.
Here are some articles that will help you pinpoint the issue.
https://www.gardeningknowhow.com/edible/fruits/citrus/leaves-falling-off-citrus-tree.htm
https://www.gardeningknowhow.com/edible/fruits/lemons/lemon-tree-leaf-drop.htm
https://www.gardeningknowhow.com/edible/fruits/lime/lime-tree-leaf-drop-why-a-lime-tree-is-losing-leaves.htm