Patchy Germination on Reseeded Lawn -- Wait or Panic?

I live in Central Kentucky. In late September, I killed off my 14,000 square foot back lawn with Roundup (65% weeds courtesy of my homebuilder).
On October 2, I reseeded with a turf type tall fescue blend (Crossfire II, Avenger and Cochise III) using a slit seeder. I applied the seed at 10 lb.+/1K sq. ft. in a criss-cross pattern and I applied Scott's Starter fertilizer at the recommended rate at the same time. I have watered and continue to water with an automatic underground irrigation system 3 times per day (about 8 minutes each watering). I first saw evidence of germination on October 8. There has been 1 1/2 days of rain so far and the temperature has been varied -- high 50's to mid 70's daytime and mid 40's to low 60's nights.
Now, germination appears to have started to take off to some extent as there are seedlings up to 1" tall growing fairly uniformly over most of the yard, but I have 3 or 4 fairly large areas and several smaller patches that show no evidence of germination. One area is a rather large (about 10' X 70')strip in the very back of my lawn. I can discern no real difference in the amount of water, soil conditions, etc. between the areas showing germination and those where there is no germination -- the "bare" areas are directly adjacent to those showing germination.
My questions are these:
What could have caused this patchy germination?
Should I reseed the bare areas now?
Should I give the bare areas more time to germinate? If so, how long? Should I then reseed after waiting?
Any help is much appreciated!
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It normally takes about a week for tall fescue to germinate. So, I wouldn't be too worried yet, and certainly wouldn't seed again now. It's possible that the areas that have not come up yet are cooler, maybe less sun, or more wind causing cooling through water evaporation, which would slow germination. Were those areas treated with any herbicides other than Roundup? With Roundup, its recommended to wait a minimum of a week before re-seeding, which I hope you did.
If you don't see growth in another week, then I'd take up a square foot of soil and carefully start investigating to see if there is any sign of germination. If there isn't then I would seed it again. You'd be near the end of the seeding window at that point, but should still have enough time for it to take.
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Thanks for your reply. I used only Roundup and waited at least a weed before seeding. I'll continue to wait and watch.
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The farmers in my area spray roundup and seed on the same day. I don't think you need to wait but I'd be interested in other opinions from better educated folks than myself.
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