I'm not sure if I'm having the same problem because there is not much feedback, but what I do notice or try (at least when I'm conscious) is vary the level of politeness and directness of words between characters depending on their background.
It reminded me of a story where the POV trio are so, so, distinguishable from each other. Granted, there is the power of language on his side, cause the story is meant to be understood by bilingual readers. The speech is distinguishable because you know who speaks in English most of the time, the other uses mostly code-mixed English, and the other speaks mostly in Filipino.
He had one character who had the most cussing in different languages and generally sarcastic, and mostly has almost rhyming, good-sounding dialogues.
The other character is polite, more asking than demanding, and speaks the least English.
The other speaks almost like a dictionary, cold, and overly-logical in his speech. Uses the most English, I think.
This person tried writing out only dialogue without naming who is speaking and you could immediately tell who is speaking what. Could that be a good exercise? Or at least a way to assess yourself? Just a random thought.
Building on what @cherrystark said, an artist might notice the composition and colors when entering a room while a penny-pinching person might mentally calculate the cost of renovating the room.