DM wasn't sure what lights may have been on, but from the crime scene photos we can see that there was a big string of fairy lights that went up the corner above X's bed, across the west wall of her room (the wall opposite X's bedroom door) and down the wall of the corner behind her mirror that was near the bedroom window.
Other crime scene photo looking down the hall from the living room to X's room shows the 2nd floor bathroom light was off. Other photos also show that the little glass and metal drinks table near the hallway to X;s room had twinkly lights turned on as well as the Good Vibes sign's lights. The cascading fairy lights behind the east wall of the living room were on, the back patio hanging string of lights were on, and it appears that there was a string of fairy lights that go across the half wall at the top of the 3rd floor landing that look to be turned on (those probably would have been visible from the middle front window on the 3rd floor (DD driver could have seen the glow.
From the girls' social media and videos, we see Maddie had fairy lights in her room that outlined her closet and then came back up at least one side of her window.
At least from the crime scene photos, it looks like Dylan didn't have any fairy lights turned on that nor did Bethany.
There may have also been fairy light on in the kitchen in that area where they had their table...I swear I saw some on a social media post of theirs.