It’s my understanding is there are only a handful of reason
1.male-female pollenation (doesn’t have to be weed pollen either)
2.hermie from rhodelisation
3.apomixis
Environment can play a role and so can genetics. Seeds created by a hermaphrodite are more prone to passing along the trait. Autos left to mature too long with spontaneously seed (happened to me)
If they were all seeded like that I would think they were pollenated because one speck of pollen makes one seed. Were they indoor in a tent? If so one may have hermied @Myfriendis410 when yours produced its own seeds was it that many seeds or just a few?
In my case I had 4 autos and a photo. 3 of the autos developed seeds. One of them quite a few. The photo had none along with one auto. All side by side.