Young citrus sudden leaves drop

evg1 starts with ...
Hi,
I have a young dual grafted orange/mandarin tree growing in my backyard in Sydney West. It was great looking tree with young flush growth and lots of flowers started to appear in August. Since it was first year it was planted, I decided to remove all flower buds to promote tree growth. What happened very shortly after is most of leaves dropped on weaker half of the tree and most of the branches started drying out there.
Could it be caused by my flower removal? Did I remove them early or incorrectly? Or could it be just a coincidence?
The soil in general is heavy clay but I planted the tree in new planting mix. It is also elevated to prevent overwatering.
I attached some photos. Please advise!

Pictures - Click to enlarge
Picture: 1	Picture: 2