I think that my plants were given too much nutrien...

Hey man I hate to say it but your plant is beyond repair. All of your fan leaves are gone so it wont be able to process enough nutrients to produce good flowers. With an autoflower there is no time to repair it. I would cut your losses and start over with new plants. Everything looked great at week 5 but something with the feed, lighting, or watering went wrong and she it toast. Sorry

Honestly seeing the auto flowering aspect I would say good luck she is pretty jacked up I'd do florakleen gets rid of salt build up or keep running plained ph water and then start nutes at super low levels and bring up incrementally, they have really taken a beating and all good intentions aside they may be really messed up and not give you much, keep going but ya good luck.m

If you think its a nutrient build up, have you tried flushing it with a flushing solution? Other than that, fresh soil may help