I recently bought a Mr. Mac Satsuma Mandarin orange tree about a month ago. When I bought it, it had lots of small oranges on the tree. I just lost the very last orange left on the tree today. I left it in its original pot for a couple of weeks and when I noticed it was losing its oranges I transferred it to a larger pot about 3 to 4 inches bigger. When I did that I used Miracle Grow's citrus soil and the loose soil that was left from the tree mixed together. It gets about 5 hours of direct sunlight and faces west , SW. I live in an apartment so thats all I can get. I water it whenever it feels dry a couple of inches below the surface which is about 2 times a week whenever it doesn't rain. I live central TX where we get rain about once a week right now with the humidity staying around 60%. Its been cloudy for weeks now with a day or two of sunshine with temps around 80-90 degrees F. I try to fertilize it every time I water. I use Nutri Star citrus fertilizer (12-10-10). Any ideas on what could have been the problem that caused my oranges to fall off? Any tips on how to make it create a lot oranges? In the pic,the leaves in the pot arn't from the orange tree but from another I just finished trimming.