This was my first extract batch where I used a yeast starter, making a Black IPA. I did the calculations to create as appropriate a starter as I could for this 1.075 beer, used a stir plate for 20 hours, put it in the fridge for a day, made the wort exactly as I had my previous beer which have been turning out quite well, decanted the starter, and poured it in. If anything the OG was a bit under the target, more like 1.071.
I saw a very healthy krausen kick up within about 8 hours of the fermentation, it was bubbling away furiously and then about 2 days later started to fall back down. I was a little disappointed that the fermentation was done so quick, thought that was a bad sign. Then about 12 hours later a "cleaner looking" krausen started to rise. I'm almost 4 days into the fermentation now and this newer Krausen is even taller than the first one I saw. I am pretty meticulous about sanitization and cleaning, and cant think of anything that I did differently in this batch aside from the yeast starter that would have infected it. Any ideas on what might be going on?