Both the curds and whey are probiotic so if the whey agrees with you more I would definitely stick with that for the time being. I read in your other post that you have sinus issues and I’m wondering if that could be connected to a dairy intolerance? Which may further explain why the curds don’t agree with you. Just an idea of course.
I wash my grains under the tap each time and this certainly does not seem to have had any detrimental effect on them (if anything theres far too many). I find if I don’t wash them they begin to smell which gets lots of complaints from my household and puts me off.
I can’t see why not you won’t be damaging the grains by doing this but I am no kefir expert.