If 2 ducts are not heating out of 7, then, the heating furnace is working. It is likely some clogging in the other two ducks or leaking, or the connection fell off somewhere. I had a couple of ducks (those flexible duct) fell off underneath crawspace before, I just taped them together with the heating duct tape. I also had housing mice stocked stuff in the flexible duct before too.
You need to trace it step by step to see what is wrong if you want to check it out yourself.
