Knowing your location would be helpful. Also, a picture of one of the runners on a plain background would be good. From the fuzzy picture a couple of shots in the dark to compare to are nimblewill, Muhlenbergia shreberi or torpedo grass, Panicum repens.

If you want pure fescue, you'd have to renovate. Personally, I don't see any need to do so as that can be a very nice lawn if you work on it a bit. >>What about the yard leads you to believe it's low on resources? I did have the soil pH tested which came out at about 6.8-7. I know the yard was limed a year or so ago. And no doubt it needs feeding from what I understand of the previous owners maintenance routine The slight patchiness, the inconsistent colors, and the differential in growth rates still apparent from late fall. There are more subtle signals like the way the grass' blades spread that point to issues with lesser nutrients and micro-nutrients in your soil. None of that is assured, but it's an indicator that you should have this soil tested and then rebalance it properly--don't blindly throw lime or anything else (other than nitrogen or organic feeding) at a lawn or garden. Improperly balancing the resources is worse than being too low on some as resources compete with each other. Overdoing calcium would, for instance, block absorption of phosphorus, potassium, and most minor elements. >>I was thinking I had a good enough base to overseed with fescue or KBG/fescue mix without having to completely kill off the lawn. Would you agree or disagree if I am wanting to go with that grass choice? Partial disagreement. Everybody tries to get around the soil test, at least until they see photos of lawns that have had them done, fixed any issues, and then used proper care techniques otherwise. Even cheap, builder's grade lawns look fantastic. Properly chosen seed for the locale stops passing cars to admire the greenery. There are few existing lawns that can't be rescued to become extremely impressive. But if you have your heart set on one particular grass type, a full renovation is going to be the only way to achieve that. Since it can't be done until late summer, that gives you the rest of spring and summer to fix any soil problems.

here are few more photos these are in my backyard. seem like the same plant. 1st one is 7 inches tall and the other 2 photos seems like the same plant but fully matured.

Chickweed, Stellaria media, a cool weather annual weed. Very easily pulled up but do it before it goes to seed!! Also edible if you care to get rid of it that way :-)