What's causing uneven hair growth after hair transplant? (photos)

I had FUE hair transplant surgery 5 months ago. Hair growth started by the end of the third month. However there is obvious difference between right side and left side in growth. The implant was done by 2 persons and I feel that the difference may be because bad technique of one of them as the difference is sharp. What I should do now? The doctor says that this difference is blood supply related.