You can't blame those broken bows on low moisture content of the wood until you inconclusively determine the wood MC is indeed too low. You just have to get a humidity meter (costs only a few bucks) and place it in the room where you store your bows in. Monitor the RH in that room for a few subsequent days, at various time points. Only then you can find out what the RH is, so what the EMC of the wood is.
If it turns out to be a problem with the wood being too dry, find a way to increase the moisture content of the wood. Nothing wrong with kiln dried wood by itself, as long as you treat it right.