Maybe you daffed out and capped a screw top. But that probably wouldn't have had any carbonation, so probably not that. Sometimes I've heard of people dumping their boiled priming sugar into the bottle bucket but not giving it a good stir. The heavy sugar stayed on the bottom causing the first bottles to pop (explode) while others were totally flat. Doesn't seem like that happened here. If you stored them in different places in the house then it could be a temperature issue. Some may have been too cool to condition properly, but I get the impression you stored them all together.
I've had infections where the later bottles were gushers because something in there was creating gas. But you had the opposite problem. I've also had infections where they went from just right, to kind of tinny, to gusher. If the next few are tinny or gushers, it might be that. Infections are easy enough to recognize. Hold the tilted bottle up to the light and look for a ring in the neck. That means something unwanted is growing in there. If that's the case, search this site for sanitation. There's plenty of good threads.
Most likely the cap wasn't on right. Sometimes it doesn't make a good seal and some of the pressure gets out. Could be user error or a defective part. If you're using Grolsch type bottles you can replace the gaskets. Maybe be a bit more mindful when crimping the thing to be sure that it's on right, but if we're talking one bottle out of how many batches... I wouldn't worry about it.
