Krausen fell and returned days later

So I'm brewing an "old fezziwig clone" who knows?! Recipe seems solid and smells great. So day 2 of fermentation had a slow start but healthy krausen by end of the day, about 5-6 inches. Lots of air lock activity.
Krausen fell completely after maybe 6-7 days.
So after about a week of letting it settle and planning on racking to secondary there was a little foam on top again. 2 days later its slowly growing probably not even half an inch of krausen but with steady air lock activity. Looking into the carboy there is clearly some activity from the depths of the wort.
So what's happening? Why is it fermenting again? Temp change perhaps? Its just sitting at ambient room temp, around 68-72°
Any advice is welcome

what's your OG and FG?

OG was 1.064. Have yet to take a Gravity reading after fermentation because I'm not sure its done

Anybody wanna chime in ?

So you haven't racked it? I have never had zombie krausen, but it probably isn't good :cross: lol.

Hmm. I mean it smells normal. Looks normal. I'm crossing my fingers.

all this is based off OG and FG. without those you are blind, just looking at foam

Agreed. I just figured I'd wait to take a reading until it was gone.

I have not seen it either.
What yeast strain?

I am guessing you had an under-attenuated fermentation, then when you racked, the oxygen re-energized the yeast.
I think if anything I would think it's a good thing. It means that oxygen got eaten instead of oxidizing your beer.

(edit - Oh, you did not rack. I dunno)

Wyeast 1084 Irish ale. Yeah didn't rack yet

I had a krausen resurrection once after raising the fermentation chamber temp about 5º F once. It was enough to blow out thru the airlock in a bucket with pretty good head space! Apparently the temp rise got the yeast all excited again. Beer came out fine.

Brew on

I typically see this when raising the ferm temp as well. I typically ferment in the 62F range but I'll raise the temps up to 68 after about 7-10 days to give the yeast a little bump.. I have seen a double krausen before typically on higher OG beers.

That sounds about like what happened, my temperature has been fluctuating and it did go higher.