Hi guys,
First off, thanks for taking the time to read and help me.
I am located in Calgary Alberta Canada. I received this neglected lawn from the previous home owner in a pretty bad shape. Started the season battling clover and dandelions. Now those are gone, I have been seeing these patchy clumping grass. From my googling, I think it is clumping tall fescue.

Can you guys confirm and suggest ways to fix this? So far I have been spraying Roundup on the big clumps and re-seeding.there still some random spots where clumps are forming with time. I fear that this is a band-aid fix and the fescue will come back in clumps. Will I eventually need to kill the entire lawn with Roundup and reseed all at once?

Thanks