Hello from Center Italy!
I have a female pistachio's plant bought 3 years ago.
I had it in a tray for a year and in 2014 I planted it.
I noticed that it didn't grew up a lot, only about 5cm (2") in a growing season.
It has a bigger trunk diameter but it didn't grew in height a lot!
I also planted some rootstock (p. terebinthus) and they grew very well!
I know that it was grafted on UCB#1 but according to me it is not and it is actually a p. terebinthus rootstock.
I use to fertilize it with manure and chemical balanced fertilizer.
In spring it seems to be a very good plant but the last two years leaves used to fall too early, and according to me this is the problem.
I don't know if it has a disease!
Anyway, do you know what can it be?