To flush or not to flush is another great forum debate, smart people on both sides can convince you one way or the other. Flush one plant and don’t flush another and decide for yourself.
So here is my two cents worth. The idea of "flushing" is a highly debated one. No matter which side you come down on there will be those lighting torches and running at you with pitch forks, lol. I have done a ton of reading and the main thing I found is that the best purpose for flushing is really just to correct mistakes. When growing in coco as I do there is a good time to flush the medium and that is when you have not done a great job in feeding. Many over feed the plants and if they do flushing excess nutes out of the medium can be useful to get their feeding corrected. Keep in mind this is more for correcting the medium they are growing in and not about flushing things from the plants themselves. Take the time to learn to read the plants and they will tell you what they need. It is the same with runoff ppm, I believe that is more for coco growers than soil. Your plants look nice and healthy, don't over think things too much and keep doing what you are doing. Welcome to RIU, you will find many wonderful people here with real experience to help guide you. Good luck and happy growing.