My 2 Year Old Daughter Tested Positive For Thc While

My 2 year old daughter tested positive for thc while with her father...carboxy-thc Initial=.05pg/mg Quantative=.11pg/mg and native-thc Initial 10pg/mg and Quantative=37pg/mg on June 25, 2016. I am trying to prove that I had nothing to do with that, 4 days later on June 29, 2016 her father had me tested and my Initial=1pg/mg and Quantitaive=0.1pg/mg. So I guess my question is what would have been done to her for her to get those levels in her system? Also, I had another drug test on August 11, 2016 and it had the same test results as before but was labeled Negative whereas my first one was labeled positive, any idea why? All were hair follicles. I am 5'3", weigh 130 lbs and am 36. I quit smoking May 24, 2016