Its the alkalinity of the soil that's stunting the tree. If the soil has the wrong pH, a plant can't utilize the nutrients in the soil. You are going to have to lower the pH before your tree is happy. Do you know the pH of your soil?
Have you fertilized your tree? If so, with what? They are very exacting in their nutrient needs so you should always use citrus fertilizer (3 or 4 times a year). You can also use iron sulfate or soil sulfur but, just once or twice a year.
But to jump start the pH lowering process, use a fertilizer high in acid, like Camellia food. Use it sparingly, maybe half strength, you can always add more but its hard to take it back out of the soil. Top dress the soil around the tree with a couple inches of milled peat every fall. Winter rains will help wash the acidity down into the soil.
