Yea see if you can raise it and if they’ll all start going under.
With 6 your brooder might get tight in a few weeks. You may have to come up with a new set up. Where abouts do you live, I’m asking as far as weather conditions and temps? And how long did you plan on having them inside?
I know some people keep them in for 8 weeks, I’ve never done that long and try to plan my ducklings around warmer temps here that way they can go outside way sooner, even if just during the day. I know this is unpopular opinion and I’m not telling you to do this, just telling you what I do, mine are usually fully outside by 3 ish weeks. Again based on temps and conditions.