Immunizations

So I was hired at a peds office in Nov and I started doing immunizations a few weeks after I was hired. In Feb I asked for a mini eval to see how things were going and I was told I needed to be doing injections alone by my 90 day mark.  Well I wasnt I still had someone with me and was getting positive feed back after but at 90 days I was let go and they stated it was because "they don't feel comfortable with me goving the injections alone". 
They allowed me to continue to give the injections for the month(w/positive feedback) without having me "retrain on proper injection administration, like watching someone else for a few. 
I honestly feel like I was let go because on of the doctors didn't like me for some reason, she always had an attitude with me and only me, and the other doctors were fine with me. 
I guess Im just wondering if this makes since, if Im not doimg I jections correctly but they continued to allow me to do them for a month without "retraining"?