1 In general, the total dissolved solids concentration is the sum of the cations (positively charged) and anions (negatively charged) ions in the water.  Parts per Million (ppm) is the weight-to-weight ratio of any ion to water.
If you refrigerate the rice, and you want to eat it cold, its perfectly fine. People eat cold rice salads all the time. Cold rice pudding is fine. Its just sitting around at room temperature that is the problem.
Eating a dinner the night before with a spinach salad would be an excellent way to get that kind of change. Anomalies like this will happen from time to time. If you see it continue at that lower level in spite of avoiding vitamin K rich foods, then talk to your doctor about adjusting your medication.