Pictures would help to determine plan of repot. Is the soil old. Is the tree rootbound. What rootstock is it on. Do you need to repot. What variety is it. Example
Seville sour orange rootstock with a New Zealand lemonade tree. Soil is now 3 years old planted in 4 part compost from compost pile and 1 part Perlite. Bud was grafted 5.5 months ago by T-Bud method by Myself.
There are people that know a lot more about citrus trees than i do that can help You and myself out on this kind of question. I am interested to.