Lemon Tree help

I planted a dwarf lemon tree one year ago and it has not grown at all and hasn't produced any fruit. The leaves recently started turning yellow in color so I was told @ my local nursery to add iron to the soil, which I did. The leaves perked up for awhile but are now back to looking yellow and droopy. Last week I noticed a white powder on the backs of some leaves that I assumed was a mildew.
We had small blossoms this spring and little lemon buds popped out but have grown no bigger than a very small lime.
What would you suggest I do for the tree to help it to grow and become healthy? Thanks in advance for any advice!

Zone 9, Southern California and it's been HOT! :eek: