Growing Oranges or Grapefruits on STX

I have an orange and a tangerine tree, both appear to be struggling during this dry period . . . nothing really happening on either. Some new leaf shoots but also some curling leaves.
When we first "met" the house (12/07) both had a reasonable amount of fruit, but sour. They tooks a full year to perfectly ripen and we picked both trees clean this past December , even took some back home for freinds to enjoy . . . they were awesome! Throughout the year I would use the sour fruit like I would lemons/limes.

I've had lime trees for years and they do great. They do need to be watered in the dry season though and when flowering especially. My sour orange tree usually does really well but this year Omar did it some damage so it is struggling now. I was just given a gift of a great grapefruit tree and a large lime tree (the limes, not the tree). They are only 3 feet tall but both had baby fruits on them already (Crucian Garden). I'm going to make sure they get planted in some great soil and treated nicely over the summer... then... they will likely do great without a lot of care. Citrus does well on the island in general. Orange Grove is supposedly called Orange Grove for a reason... it used to be a huge orchard!

We have all kinds of citrus trees (grapefruit, orange and lime) on our property. They started producing fruit in December, which took a few months to ripen. But, the fruit is awesome. We live in an area that gets a good amount of rain, which helps. And, I have plastic containers in my sink for washing & rinsing dishes. When I'm finished, I empty the water on the trees everyday.

The oranges are especially juicy - and I'm made a lot of orange juice from them. The only problem I've had is some kind of black film (it looks like dirt) that covers some of the leaves. I believe it's some kind of a fungus, but it hasn't affected the flavor of the fruit in anyway. If anyone knows what this black stuff is and how to get rid of it, I'd love some help too.

A couple of my citrus have the black fungus on the leaves as well. I am having a hard time getting fruit because the deer keep eating my trees. I have finally put a wire mesh around the limes which they seem to like the best.

I purchased a red grapefruit tree from dept of ag and asked how soon I would have fruit. It was iin a one gallon pot and the man helping me said about 3 years. I planted it in Dec. I think and it already has grapefruit the size of oranges.
Deep watering weekly.