They say never admit your weaknesses, if you are determined to address your GPA in your PS, then only focus on the positives: 1) what you learned from it, 2) how you coped with the situation better than most ppl would have. Try to avoid making excuses. Be sure not to over explain the reasons, I would give it 4 or 5 sentences tops. Focus your PS on more positive aspects, such as your WE and EC.