Dead fermentation resurrected - questions...

Hi All.
OK, so my first ever two batches of beer are one week into fermentation: an American IPA and a North German Alt-ish no-recipe experiment. IPA is rocking along; most of the Alt as well. But upon close inspection this morning one jug looked "wrong". The others were active, with supertiny bubbles rising happily and a layer of them under the Krausen. Number five had no life to it. The bubbles were much bigger (maybe 1/2 mm) and absolutely still - looked like stagnant pond scum. The fermentation setup for my Alt is a hillbilly mishmash of (ultrasanitized) half gallon and 1 gallon glass bottles. Two jugs have proper bungs and airlocks. One has an aluminum foil cap with an airlock popped straight through the foil; one has a foil cap with little airholes poked in it. The problem jar had a plastic cap with bung and airlock. I took these off and found the cap dripping with condensation and the airlock completely blocked with yeasty goo. But NO off odor, just yeasty/hoppy. I took a gravity reading. OG was 1.040; today it was 1.014 - my intention was 1.010, and the others are still chugging away, most likely heading that direction. I gently rocked the bottle until all the pondscum bubbles popped and the krausen dropped. Then recapped with foil, cocked a bit so gas can escape. For grins I left the sample in the test jar and put a little foil cap on that as well. (Scrupulous sanitizing was practiced throughout these proceedings.) So: this evening the problem jar looks like the others - tiny bubbles rising, a nice golden 1/2 inch thick Krausen on top. Looks like a living thing again. The sample in the test jar, likewise, is cheerfully bubbling. Whatever I did seems to have worked - but can anyone tell me exactly what happened? This was a very active fermentation - one of the other jugs blew the airlock off. I resanitized and replaced it, and it's AOK, back to blip blip blip. Jug # 5 just plugged its airlock up and then ground to a halt. But why? Why wouldn't the pressure have built and blown the top off as with the other jar? Why did it go so still? Why and how has it resumed fermentation? And is it likely to finish correctly, or has that temporary stagnation wrecked it? Thanks for any feedback.

 

I pitched before I distributed, and kept the wort pretty agitated throughout. The only difference in behavior occurred when the airlock on bottle 5 got blocked - then everything ground to a halt. And now, unblocked, it's active again. I just don't get it... I know open fermentation is still practiced. Isn't that sort of what I have going on with three of the bottles? Could be interesting... But OK, I'll keep my mitts off it for another week. I'm a half-batch brewer (ha! - can I call myself a Brewer with only two batches under my belt?) Really hoping Santa brings me another lovely little 3 gallon carboy / bung / airlock setup. If I'd had two I never would have resorted to milk bottles.