Can ~5% weight loss over 6-months be caused by nutritional iron deficiency anemia (hb 11.1, pcv 35.4, rbc 3.75, ferritin 39) for 57+ yr female ?

Same cause for both: It is likely that the weight loss and anemia are being caused by the same entity/disorder. It may be poor nutrition, malabsorption, parasitic infestation or an undiagnosed illness. It would be prudent to see a doctor for an in-person evaluation. Iron deficiency anemia in an adult male is always a concern for bleeding in the intestine.