Ya it's amazing how much of a difference flushing your plants can make a difference, esp if you immedietely identify the problem and react quickly. Doesn't look like you allowed much damage to your plant. It will thrive without a couple dead fan lower fan leaves.
I would highly consider an upgrade in nutrients. Cannabis specific nutes would be best, and my personal preference is organics, but it's all about finding what works best for you. Don't buy anything that can be potentially confusing to you. And feel free to grab a bunch of small bottles of various products and test them out. Certainly nothing that you can do overnight.
Best of luck!