Sorry for late reply - bad form!
Ketones are what the body uses for fuel - it breaks down fat to make them so not by-products. You lose excess ketones when in ketosis which is why we pee pink, but when your body gets a load of carbs it dumps the ketones it was holding onto to run the body and switches to the new source of energy you gave it. So at that point you might even pee purple and think all is fine but it isn't the true picture. Now, whether that matters is another thing. If you are still losing weight perhaps it doesn't, but if it is important for you to be in ketosis (with the appetite suppressant effect) then it is worth bearing in mind.
Even if you aren't peeing pink you can be in ketosis if your carb level is low enough - it just means you are drinking plenty of water and/or don't have any excess to get rid of. Years ago on an Atkins type diet I was doing really well and then had an unavoidable curry (would have offended boss) and tested as soon as I got home. Thought I was home and dry as the stick was so dark but then I researched and realise that it was my body coming out of ketosis, dumping ketones and munching on curry. Always remembered it!