accelerating universe conundrum, help me find my logic flaw please

Help me find my error in logic here please. The current theory is that
the rate of acceleration of the universe is growing with time. The
experimental data to support that is class 1a supernova at large
distances are dimmer than expected. The expected brightness is from the
red shift of the supernova. Since they are dimmer than expected that
means they are further away than expected. Now, to me, that would mean
if they are further away than you would expect from their speed, as
measured by red shift, than in the past they must have been traveling
faster than they are now in order to travel a greater distance. But the
conclusion current theorists reach is they were traveling slower in the
past and are moving faster now. So where is the flaw in my reasoning?
Thanks ,
Chas