Decreased erythropoiesis would indeed lead to decreased red blood cell count and hence decrease oxygen-carrying capacity, but it mainly manifests as pallor and not cyanosis.

Increased hemoglobin affinity for oxygen might paradoxically worsen tissue hypoxia because hemoglobin holds onto oxygen tightly, not allowing it to release into tissues. However, this condition does not typically cause cyanosis until the hypoxia is severe.

In this patient, the most probable cause of cyanosis (blue discoloration) is a shift in the oxygen-hemoglobin dissociation curve, decreasing the hemoglobin's affinity for oxygen. This decrease in affinity means that hemoglobin is not as eager to bind oxygen, translating to less oxygen being carried to the tissues, leading to hypoxia and subsequently cyanosis.

Reduced cardiac output can lead to poor tissue oxygenation, but it wouldn't present as isolated cyanosis without other signs such as breathlessness or chest pain. Also, hypoxia due to reduced cardiac output does not usually cause cyanosis unless it's severe.