were the grains crushed at the same time or just prior to each brew session? if they were crushed at the same time, the later brew grains would not be near as fresh and probably dried out more.
the higher mash temp would have lended a more dextrinous wort, therefore a brew w/ more body. so it's not that one......
maybe it was the longer secondary as Dude suggested?
sounds like you force carb'd. u did have the co2 hooked up to the down-tube hu? i've done it before, and couldn't for the life of me figure out why my beer was flat and had no "body" due to lack of carbonation...... :~)