Posted: 08/08/2017 at 08:26
I assume you used a general weed killer, not a lawn weed killer (i.e. kills weeds not grass) ? Have a look what you used and what it says it will do. what product was it and how much did you use?
I wouldn't have thought its spreading as such, just it takes time for the weed killer to get down to the roots and kill the plant. I wouldn't have thought water would help at this stage if the plant has had a blast of glyphosate some days ago.
Not sure what the birds are up to, they have their own agenda.
you will probably have to treat each patch, getting out the dead, add compost, reseed, but there are plenty lawn experts on here who will tell you the best way forward.