My 8 year old Cockatiel started showing periodic signs of illness, weakness, loss of balance. He is eating and drinking. Took him to the neighborhood veterinarian, vet originally thought it was a sign of organ failure, blood test revealed anemia, not organ failure. Started him on B-12 injections weekly, had his third shot last Thursday. At first he seemed to improve, but the symptoms return every few days, usually in the morning shortly after I get him up from his 12 hours of sleep. He will appear exhausted, when he should be investigating the day. Often I'll take him on my lap and he'll just collapse for about an hour. Later in the day he seems mostly normal. He's about due for another blood test. Do you guys have any ideas?