Penn Herb is building a new store at the corner of 2nd and Spring Garden! They have a sign up on the building with a picture of a 3-story building, with an expanded retail space for them. I checked their website (http://www.pennherb.com/LibertiesGateway) and it has more details: "The new building, known as Liberties Gateway, will be a three story mixed-use building totaling 35,000 sq. ft. In addition to the Penn Herb flagship store, there will be additional commercial space available as well as boutique apartments."
The zoning archive for the project can be viewed here: http://www.phila.gov/zoningarchive/Preview.aspx?address=601-603%20N%2002ND%20ST&&docType=ZONING&numofPages=26&docID=151065&app=027
The business must be doing well, good for them!