I came across a thread the other day where someone mentioned that CIC may check with the PCC's country of issuance's police/legal department before passing the criminality check. In that case, your criminality check will be on hold until CIC receives a response. I don't know if they do it for certain countries or they do it randomly.
Also keep in mind that you were requested for additional documents which you submitted on 25/4/2017. This may add at least a month of delay to your application. I too was requested for documents in mid Feb and submitted them by late Feb. There was no movement on my application after until May 15.
Anyways, I hope you pass BG IP1 soon.