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Sorry if I misunderstood at all but here's a shot. 1. If you merged both pages I assumed you changed the url of at least one of them. Did you delete the old 'b' page? It may of had links to it that were helping you rank for it. Also, make sure the page titles are still as relevant as the old ones. 2. If the links were to page b and page b was deleted it won't really help unless you 301 it or create it  again. I see you recreated them, did you keep the original url structure or did you change it? I would make sure that you have all the pages 301'd to the new ones you want to rank. If you really were penalized you would get a notice in webmaster tools, otherwise it's just the algo change. Google also changed a lot of things in the past two months so it may have to do with that more than with the changes you made. Overall, just make sure that all your pages are redirected properly and hopefully you'll gain back those rankings. If you have any really shady links I would try to get them removed if not, it isn't a huge deal. Good luck!