Fake grass is awful you might as well stick an old carpet across the garden. We’re supporting biodiversity!
In all seriousness though I think there are like 5 different “species” of grass in my garden, it grows at totally different rates, and then there was a big patch that the dog had burned away with piss that I raked out and put “dog repair” seed on (my one but of gardening this year) and it worked great EXCEPT THAT the grass that grew there is a really lush, deep, healthy green and the rest of the grass - after all this horrible sunshine - is a totally different colour of light green

.
Might just chuck what’s left of the seed around all over the place and see what happens…