Hi Fuzzwah,
Currently, VisualWget was programmed in this way, if the first
download started, it get all available bandwidth. Then if the second
download start, it will get the bandwidth only when the speed of the
first download was dropped.
But when the first download finished the second download should take
all the available bandwidth (I just test it again but I cannot
reproduced your issue). I'm not so sure, but I think this may be the
server issue. Maybe we can make the download to auto restart if speed
drop to below (let say) 50 percent of available bandwidth.