In that sentence, "concrete issues" and "specific issues" are basically the same thing. People use the terms interchangeably most of the time. That said, there is a difference. "Concrete" in this context means "not general or abstract." "Specific" can mean both "explicitly stated" and "limited or detailed." For example: General issue: transportation is a problem here Concrete solution: build a road Specific solution: build a road from this hill to that river I hope that helps!