What I THINK you are referring to is probably not the fault of the chromes. I am hearing a bit of "clack".
You have to keep in mind that flats have a much larger "footprint" on the fret than rounds. The round wound string touches the fret only with the pin point contact of the round winding. The flat touches with the whole width of the crowned fret. This means fretting accuracy is very important. As well, you may have to adjust your attack location to slightly back of where it was when the problem occurred. It is much more difficult to play flats WELL than rounds, which are pretty forgiving.
The chromes will accentuate mis-fretting because of the prominent overtones they have when new.
B.
Edit: I want to stress here that the mis-fretting I refer to is NOT related to finger pressure on the strings. It's the location behind the fret that is important. With a bit more tension of most flats you are able to lower the action a bit and still get good playing comfort. Don't let this string stiffness issue scare you. It just requires getting familiar & adjusting setup a tad if it suits you.