I planted 3 pounds of 3 year old rootlets from a notable well-established dealer, when I first got started. The results were mixed, only had about 70% to come up. Planted them in good places, and in two different locations.
I have a deer problem. one of the patches i planted was very near and adjoining a major deer trail. I should not have planted them there, and deer browsing cleaned them our every year. the othe patch was smaller, and these did not come up at all.
this winter, when manicuring the patches, I fenced off the major deer trail area so that it was impassable to the four-footed suckers. What a surprise that this spring, and since the deer do not come thru this place anymore, that my original rootlets were above ground! almost all of them survived after having had their tops eaten.
Grower - 1; deer - 0!
Stunted above ground growth can also be due to soil imbalances, however you do not mention what your soils analysis is there where you have these planted.
I think I would have to contact the place you bought these from and discuss the problem.