4 minutes  for 3 squares away does seem excessive.

I cannot recall going out of my way to boost the speed of troops, my slowest ones do not take that long but I do not have any history of how or if their speed has changed.

Maybe there is someone with the information that you need and will post an answer for you.

It might help if you were more specific,on which troops you mean, and what upgrading to troop speed  you have actually done.

There are many many ways to increase troops speed the fleetness knowledge is a little part of it but it all helps.

Have you looked at things like equiptment and gems to increase march speed as well?,also things like vip level(after a certian level ) and town skins will make you marches quicker.

There is also marching speed increases in your hero set skills

Also moveing west to east or east to west is a lot quicker than marching north to south or south to north,hope this helps a little

What tier are you sending? t1, t2 … t7?

It does sound like 4 mins for 3 squares is t7 siege sort of speed. 

There used to be the 30 minutes 25% marching speed increase  and 15 minutes 50% marching speed increase won in competitions. 

Now you tend to see the 25% March time reduction or 50% march time reduction.

T1 troops are the fastest and they get slower as the troop levels get higher.