I bet you got more rain than we did this year. The heat and dry here has made it tough on my 3 leafers, some look OK, some have just passed on from the heat/dry.
You may want to consider spacing yours out a little more.
You could transplant some of those that are bunched up late in the year, either this year or next. As long as they are looking healthy would probably be Ok to wait until next fall to transplant to thin them out some.
Scotts book says to plant at 4-5 seeds per sq ft, and you should end up with 1-2 per sq ft at maturity. Looks like some of yours is a bit thicker than that.
i thought bout that when i put the seeds out , i put out around a 1/4 pound of seed on another part of this property and about a month after i did it they came through and pretty much clear cut it , so i never did find those, but i did get lucky, i covered a rock thats about 5 foot off the ground and around 8 ft by 10 ft in size with seeds , the rock had maybe 2 or 3 inches of coal black dirt on it and id guess 90% of those seeds came up