plant/replant perennial

my jerusalem artichoke harvest is so small compared to previous years ( and just as a side note, my one experiment in growing sunchokes in a well watered container produced exactly six smallish tubers...weather or container size? ) that i am left wondering if it was the heat and drought or if the plants are loosing viability because of a limited number of individuals with which to swap genes...so i ordered a new batch from my organic supplier in maine and today i went to the gutted out house, cleared out a bed, and planted them to see what happens...i will be growing some individuals from this year's harvest as well just to see if the weather was the culprit...if both groups have comparable harvests i will assume climate..if not then it would seem to be a viability issue...all the fall planters are in now...the sunchokes, the wheat grass, ginseng, and the elephant garlic...the ramps have been in since august...so now we wait...march should have news.