Campden tablets are a form of potasssium (or sodium) meta bisulfite.
They are not sulfates, and they don't kill yeast. They are used at the very beginning to help prevent microbes (like bacteria) from taking hold before your chosen yeast strain can.
Thereafter, it is very common to use them when racking in order to maintain about 50 ppm of sulfites in the wine/mead/cider because it's used primarily as an antioxidant.
I tend to use campden (sulfite) at every other racking because I don't have an S02 meter to be precise, and one campden tablet per gallon at every other racking is a good guestimate of 50 ppm.
As far as sorbate, that is a preservative and is normally used only in wines that will be sweetened once fermentation is over and the wine is completely clear. It has a flavor, and I don't like it, but I almost never use it because I don't like sweet wines anyway.
One of the problems with sorbate is that it is not compatible with MLF- malolactic acid fermentation- that happens sometimes with wines. It makes a terrible reaction, ruining the wine- that's one reason it's rarely used and only at the very very end right before bottling.
If you manage to keep fermentation going, and the wine tastes ok, then it's not a problem except for the taste of the sorbate itself.
Next time, read the recipe extremely carefully and be cautious about adding anything to a fermenting wine.
