I just used a kc masterpiece marinade steakhouse for meat that I realized after eating does not bear a kosher symbol. I looked at the star k website where I found that the symbol was removed, and it is no longer certified. The kc website says they are all kosher. What happens to the kelim I used for supper now? Do they need to be thrown out or kashered? Thank you.
I do not know why the kashrus was removed, and you can ask the Star K people the reason for this. Perhaps KC have changed to a different certification. This should be ascertained.
If it is due to real kashrus problems, and the dishes were used with hot food (the more so for a keli rishon, or for a solid such as meat (Shach 94:32)), kashering would be required.
However, if the kashrus was discontinued because of some business fallout (or other reasons), and there is no reason to think that KC has started using non-kosher ingredients, the dishes do not need to be kashered/thrown out. However, the sauce should not be used until kashrus is verified.