Advice needed

We have a 7month old whippet puppy, that is completely clean in the daytime, but we are still having wee's some nights from her. We have put down newspaper and moved it nearer to the back door, we are takeing her out in the garden at 11.30pm to empty herself,   we have changed her meals and soaked her 4.30pm meal and taken up the water bowl at 8pm, and she has been clean for five nights, but this morning I came down at 7pm to a wet patch. We have had four dogs from puppys in the past and have always got them completely clean by three months. Any help would be most welcome.