Have they used a technical name to describe your enlarged red cells? If they say it's
macrocytosis, you can read about it
here. Aplastic anemia isn't listed as a direct cause, but one of the causes of macrocytosis can be chemotherapy. Did you receive ATG or another treatment for the aplastic anemia? If so, it could be residual effect of the treatment, not of the disease.
I read that the antibiotic chloramphenicol (chloramycetin) was once widely used but that once it became apparent that it could cause aplastic anemia its use was limited to only the most serious diseases, where the risk was unavoidable. It's a shame your bone marrow was damanged by chloramphenicol, even if it was the best treatment at the time.
In any case, I think it's worth asking your doctor if anything needs to be done about the larger than average red cells. Even if the answer is no, you'll appreciate the reassurance.