Sorry, I accidentally uploaded the note... I wanted to say that they have different house numbers and are of different heights. But since they are represented as one building in OSM this cannot be tagged. The building on South & Alder is numbered 1016 (probably 1018 as well) and has three floors (according to Bing Streetside), and the next one on South Street is number 1020 and has only two floors, and is the location of the Philadelphia's Magic Gardens museum. I don't know how to map buildings, but if they where created with a semi-automated tool, it might need some adjustment, because I think I saw this situation in other places as well.