What Lebmung wrote, cold can be a possibility in certain sections of the country, but not in an area such as San Diego. As to the fertilizer, I personally would not use it. Citrus are heavy feeders, more so than many other plants. I use a fertilizer with a NPK percentage of 25,5,15. Meaning 25%N, 5% P, and 15% K. Note: this is a 5-1-3 nutrient ratio fertilizer. According to the text book Citrus, and University research, this is the ratio that citrus absorb nutrients. Lastly, besides the low level of the elements NPK, many of the nutrients in your fertilizer example are oxides, instead of being sulfates.