Renee Mancino, owner of the long-running and much-loved Carrot Top Pastries committed suicide in front of her husband in the basement of her Washington Heights bakery yesterday morning.  The owner struggled with her health lately, undergoing double knee replacement in January, and then recently being diagnosed with cancer.  But her husband and co-owner Bob Macino tells the Post that he blames her death on the bakery's landlord, Presbyterian Hospital.  The Mancinos fought a $10,000 rent hike in 2010 but were faced with the potential of new rent negotiations. " Thirty years don't mean nothing.  We paid rent 31 years and you have to open up negotiations?  We broke our backs for 31 years.  We built this business...My wife killed herself right in front of me because she couldn't take it any longer."