Pregnacare original - spotting issues

I was wondering if anyone has had any problems with taking Pregnacare prenatal vitamins?
I started taking them in December mid-cycle. No issues until January my first month TTC. A week before AF I started spotting for 4/5 days until eventually AF started on the expected day. I've never had any spotting previously and I had wondered if this was implantation bleeding that didn't take.
However February came and same story spotting again a week before then AF right on time. 
The only thing I could think id changed was to take the Pregnacare so I stopped taking it and swapped the last month for Folic Acid alone and this month no spotting and AF right in time.
I have a 3 month supply of Pregnacare I'm scared to take as I'm worried the spotting could affect any chance of implantation.  I think I'd be scared to take them even if I did get a BFP
Would like to hear any experiences with Pregnacare?