US 05 yeast by Fermentis

[cetlin]

I'm using US05 for the first time and I noticed something I've never seen before. For the first five days the gas was pushing slowly the air up the fermentation lock(there was no bubbling), and now as the krausen is decreasing, the water is being slowly "sucked" towards the whole in the lid.

Is it normal?

 

[STMF]

Probably temperature change and/or change in atmospheric preassure.

 

[Nagorg]

Yes, normal and due to cooler temps post fermentation. Has nothing to do with your yeast other than them being done.