Like most things initial improvement is bigger then added improvement. As things progress incremental increase are naturally smaller. For example a jump from 5000 bbl's to 7000 bbl's was attained by more wells coming on line. With 1 well to go you won't see a 2000 bbl increase, rather most likely 300- 400 barrels from that one well and other wells adding more barrels as they become more efficient. Nothing to worry about!