Suero de leche appears to mean both "buttermilk" and "whey" which are two completely different milk products.
Is there a way to distinguish between them in Spanish?
There is, but I'm not sure how well known the distinction in terminology is.
Whey is indeed suero de leche in Spanish, and is the milk product left over from cheese production. It has a yellow-ish semi-transparent color.
Buttermilk is suero de mantequilla or mazada, and is the milk product left over from butter production, or these days more often just milk with added bacteria that generate the lactic acid (or when you're really in a pinch, milk with added lemon juice). It is whiter in color and a good bit thicker than whey or milk.
That said, as in French (where petit-leit is often used when babeurre is meant), suero de leche is frequently used mistakenly to refer to buttermilk. Perhaps, even, the mistake was brought in via the French, given their impact on the cooking world, but if you see suero de leche in a recipe, more likely than not it probably refers to buttermilk, as whey isn't commonly used in recipes these days.
In Colombia South America," it could be Kumis without sugar or leche cuajada batida. And depends of the milk if is from the farm it will have more butter. Kumis you can find it at the supermarkets but it have some sugar added. At the north at the Atlantic coast we have something called suero but it is more like sour cream and it is salty. If you need buttermilk over there ask for Kumis with or without sugar. And over here if somebody ask you for cuajada or Kumis buttermilk is close to it.