I have pretty much reached this same problem. I was in a group with many people much better than me and rapidly improved. Now I am better than all of them and my clinics have no one better than me. There are 2-3 kids that are close to my level, who might be me in a set 1 in 4 times or so we play but the rest I can pretty much beat without losing more than a couple games.
I have been dominating competitive games but I still feel like I am improving because I have gone from mainly a defensive counter puncher to an aggressive player since most of the kids are worse than me. At the same time a big problem I have is when I attack these kids there defense is much worse than when I have to play quality competition and as a result when I play a speedy player with good passing shots it is hard for me to break through him.