From your last photos all is lost. I don't believe you can turn things around with all yellow leaves. Time to replant, and start anew. You should try to find out what you did wrong first. Is your pH meter accurate? Has it been calibrated? What type of soil are you using? You may have had bugs, but I don't believe they would have killed off your plant to that extent. Follow the beginner tutorials at www.growweedeasy.com to a T and you will succeed. Good luck