You are required to obtain flood insurance on any building or mobile home that secures the loan and is located in a special flood hazard area (100-year flood plain) within a participating community. You would need insurance only on the building slightly located in the flood zone.
I suspect that the other buildings may be in a 500 year flood plain. You are not required to get flood insurance on properties in a 500-year zone, but insurance still makes sense for properties located in that zone. 30% of the flood damage typically takes place in 500-year zones.