Excessive lag times - low krausen

[zeggie]

Hey guys, I've been lazy/time-poor with my brewing recently and had 3 months off. Gotten back into it, despite not having a whole lot of spare time still, and have mostly been brewing simple pale ales and IPA's the last 4 brews (40l urn BIAB). US05 for 3 of the batches and BRY97 for one.

Now normally I get action happening within 12-24 hours and a decent krausen after 48. However all of these 4 brews I've noticed lag times of 3 days and krausen only ever a few cm high.
Beer tastes fine....none of my processes have changed. Never had this happen before, before my "hiatus". Ferment in a fridge set to 18c. Rehydrated in the correct manner (and same manner I've done the last 2 years)

Any ideas why my lag and krausen could have changed that I'm not thinking of?

 

[luggy]

How old was the yeast?

 

[Dan Pratt]

Have you calibrated the fridge temp controller, might be running lower than its reading?

 

[zeggie]

Expiry is mid next year, might of had them in the fridge about 3-6 months.

Temp in the fridge is fine, definitely 18c. Maybe should do my next batch at 20c to see?

 

[luggy]

What's your batch size

 

[BrosysBrews]

Had the same issue with some us-05 ATM, there is a thread on here about it being inconsistent ATM