Looks like KY-31 - fescue

I don't know how that started growing in my lawn. It is very coarse and clumpy.

Again, I started with 90% dwarf fescue and 10% bluegrass.

With grass seed you get what you pay for.

Read the guaranteed analysis on the grass seed bag. It might have said
89.8% Fescue
10.0% KBG
0.1% Weed
0.1% Other crop

These percentages are based on weight, not on the number of seeds. The really bad weeds seem to have microscopic seeds. It is not hard at all to get a good 10,000 bentgrass or bermuda seeds in 10 pounds of grass seed.

This wasn't grass seed. I had sod installed and the company stated 90/10.

Dchall- what was the issue about aerating that you questioned me about in another thread?