80 Yo Male - Low Magnesium, Critically Low Potassium, Low

80 yo male - low magnesium, critically low potassium, low RBC, Low hematocrit, low hemoglobin, low bun, low creatinine, Low Sodium, Low Calcium, Large Platelets abnormal, Anisocytosis abnormal, micocytosis abnormal. Has enocarditis, being treated with antibiotics. Any suggestions as to why his RBC 2.7, Hematocrit 24.4, and hemoglobin 7.9, continue to decline? Did colonoscopy and upper gi, this morning and and found no bleeding. Stool had occult blood.