My neighbor didn't have room for this small navel orange tree, so I took it (naturally ;) ) I'm no citrus doctor yet, but from looking at the web, I think the tree has some mould problem. As it is so small, I just swabbed each leaf with water diluted sodium carbonate + molasses + vermicompost and added vermicompost
around the tree. Before this I had added sheep manure and vermicompost around the tree and now there are signs of life (new buds - maybe hard to see on next photo).

What I wanted to ask - I intend to do some vermicompost tea spraying - is there anything else (organic) I should do to improve the situation ? In the third photo of a large navel tree you can see an example of what approx 10% of the leaves are covered with - (also some other citrus trees I have) not sure if it is the same problem as with the small navel or are these after effects of winter.