Can the Serpentine Belt be too tight?

I had the following work performed last week and now my engine does not spin nearly as fast while starting.

New belt
Changed water pump
changed both diff fluids
changed transfer case fluid

I have two new Interstate m 65 batteries.

I just put a full charge on them just to make sure and the truck still turns over alot slower than before the maintenance.

It's got me stumped. I can't imagine the starter getting weak at the exact time I perform all this maintenance.

Any ideas?