So do you think you are seeing nematode damage ? It can be hard to say "yes, that is nematode damage". It's very subtle. Without being right there on that turf i wouldn't want to say. You have to go by that assay and if it is only a year old then it probably hasn't changed much. You haven't reached a damaging level of nematodes so working on plant health is the right way to go. Just keep an eye on nematode levels. A yearly test should be plenty.