I have a few blood orange
trees myself [Moro and Sanguinelli] in plastic pots.
Some of the most common causes of blossom and leaf drops are
overfertilization
[ in California, citrus
trees are fertilized 3X a year from 1 to 2 years after planting, thereafter, 2X a year until maturity. fertilizer is applied between February and September. if overfertilized, water deeply to leach excess fertilizer.]
improper watering
[too much, too little. if the roots becomes too dry, followed by deep watering. try to water on a more regular basis. water when the top 3 inches of top soil is dry. ]
unseasonable changes in temperature
[a run of cold weather, followed by normal temperature, like we had experienced lately, can stress the
plant.]
pH level too acidic or too alkaline
[either one can inhibit uptake of nutrients from the roots to the leaves. check the pH. the ideal range is pH 6.0 to 6.5]