Check the data vs wifi as suggested by @jp2 as you do not want to be using data when you think you are using wifi 🙂
Another possibility for the slower wifi is that Shaw has been performing maintenance for internet at a national level (see https://community.shaw.ca/docs/DOC-16433).
I think you just solved the case! 🙂
That could explain why it appears that WiFi is slower but it would actually be slower data, WiFi speed should remain the same.
Do you have a 3G or LTE plan? PM LTE speed should be about the same as all of the major carriers. It will be identical to Telus.
I have my data turns on when I have wifi connection. I remember there is a setting to allow using data to supplement wifi at certain time which will boost my internet speed. I don't know if that has anything to do with my slowed down speed.