If you are being knocked out of fat burning altogether then you will not show ketosis. But even if you are showing ketosis (a very unreliable indicator of much anyway) this doesn't mean that you are not being affected by the sweeteners.

The best and most accurate way to answer that question is to stabilize your pattern (either with or without them) and then swap your use of them for at least two weeks while holding everything else the same. If you see a significant difference then you are being affected.

Also keep in mind that even if you aren't being affected metabolically you might be being affected psychologically. A lot of people seem to be more prone to sugar cravings if they keep feeding themselves sweet-tasting things. Behaviorally, nothing has changed and so the mind will continue to crave sweet things. As long as you can steadfastly satisfy those cravings only with sweeteners that you have determined do not affect you metabolically you are fine.