Thanks for the response.
I have spoken to the Egg Maniac and have interacted with all other eggs again (except for the one in Route 25, shown in the attached JPG).
Unfortunately i have still only got 7 eggs collected apart from the egg in Route 25.
The responses in the message box were all about that i have collected them and shouldn't collect the same egg twice.
As shown in the picture, i have tried to interact with the egg in Route 25 ,
but there isn't even an message box popped up saying as if the egg is collected or not.
It is just like a normal rock, or a tree.
Thanks!