Do double and triple hair transplanted grafts grow slower than singles?

Transplanted grafts may grow at a different rate. It does not matter if they are single hair or triple hair grafts.

Probably a followup with your world class surgeon would be the best option vs an internet forum as none of us can examine your scalp and give you a correct evaluation in regards to your concern.  However, all grafts whether 1 hair or 4 hair generally grow at the same rate based on the anagen phase/cycle of scalp hair.

How long ago was the transplant? If it is a new transplant (less than 6 months), then the likely cause of your observation is the difference in latency period (Time between when the grafts are placed and when they start growing ) that exists from one area of the head to the other. The hairline and temple points tend to grow out ahead of the other regions. It is not a matter of whether the hairs are singles, doubles or triples. The factors that can affect growth that may be indirectly related to types of grafts would include the robustness of the tissue around the grafts. More robust grafts would yield better. Also if grafts were split from their original groupings, they may not do as well as the grafts that were placed without splitting.

The rate of growth shouldn't vary significantly based on the number of hairs per follicle.  It will have more to do with the phase of each of those grafts.  You could potentially see initial differences in growth rate in different areas, but those differences should be minimal over time.  Good luck

The major question is when did you have your transplant performed?  Hair resumes growth at 3 months typically and continues in after that.  In my experience there really are very few natural single hairs in an average or better donor area so we make them by splitting the 2s, 3s, 4s, etc.  Splitting usually results in slower growth of the unnatural singles.  Furthermore, the unnatural singles typically result in a lower yield than the natural 2s, 3s, 4s, etc.  It may be that the density in the central area was higher and this impacted your circulation to the area.  I'd have your doctor check it out and if the disparity continues, the result needs to be evaluated more closely.  Again, the duration between now and the time of the transplant is of paramount importance in your history and evaluation.  Photos also help.  Still, it may be something unique to you so don't begin to panic.  

They should all grow at the same follicular rate.  The higher the percentage of doubles and triples, the higher the hair density.  

No, they should all grow at the same rate.  What most likely is the problem is that surgeons usually don't use the same density of hair when implanting hair in different areas of scalp.  Most patients benefit from haivng a higher density in the very frontal areas and it tapers as you go back.  

That is a good question and I am not aware of scientific studies on that. However in general each hair has different cycle of growth and depending on where in the cycle that particular hair is, It will then grow out. when making the units under a microscope, in triple hair units we observe that each hair may be at different stage of growth even though they are attached to each other. Also on the recipient sites, the one hair graft incisions are smaller and made closer together where as the three hair incisions are made with larger needles and a bit farther apart for circulation. so in the three hair unit areas unless all the hair grows out at the same time, it usually appears as if it's thinner and have slower growth. As time passes they reach the same cycle eventually and you should see growth in all areas uniformally.

These grafts generally grow at the same rate. Sometimes, some areas grow faster than other areas. When a hair transplant was done correctly, the number of hairs per grafts will not impact growth.