having the developer the right temp is the most critical because that controls the chemical reaction -- too warm, too much reaction and so on.
You want the rinse and fix to be close to avoid reticulation -- the emulsion swelling or shrinking and creating a crackly pattern on the film, but a couple-three or four or five degrees one way or the other isn't going to hurt. Big fast swings create problems.
temp controls contrast and amount of development, but when yu develop always at 68 you eliminate one variable--there are lots more that affect those things too. Your pics look just fine.