what is wrong with my eggfruit?

[Daintree]

I have two Pouteria campechiana in my greenhouse that are four years old. They seem to be growing well, but lately, the majority of their leaves are looking like this.
I am thinking it is a nutrient problem. 
Too much of something?
Too little?
They get Miracle Gro and Osmocote Plus. Lately, with the irrigation water getting into the greenhouse, the pot has felt a bit heavy. Too much water?
There are little specks that can be seen on the leaves, but there are no insects on them, even under a microscope. If it is something like spider mites (which I DO have in there in a very limited way), they are not showing themselves.  The white specks look like dandruff under the microscope.



Any assistance would be appreciated!

Thanks!

Carolyn

[shot]

Mites

[Daintree]

I didn't realize there were mites so  small I couldn't see them. Dang!

Thanks!!

Carolyn

[shot]

You did not catch them when they did their deed.

[Daintree]

Shame on me! I am a bad plant parent 

Carolyn