I read somewhere in the policy flapdoodle that eBay has in its messages that the change in neutral value on your feedback was something to do with the comparative value of negatives. It was a complicated mathematical formula which made no sense to me. Probably doesn't to them, either.
Of all the mean things they've done to small sellers, that was the meanest. Those neutrals did not denote the dissatisfaction of a neutral; yet now it seems to. Buyers care more about your feedback than they do about the mathematical formula eBay used to dilute or ding it, and that's what they'll go by.
Go to item #280230016844 on eBay and you can see lots of folks pointing out all the fallacies in the feedback system and how eBay has exposed the small sellers to the whims of the marketplace.
Some people say, well, B&M stores get the same thing - I say they do not! Would they for a minute put up with the abuse, the thievery, the scams that go on on eBay and now are being sanctioned, almost encouraged, by the Corporation? No way. Stores have their own ways of protection. From time to time people find their way around them but not by threatening, intimidation, coersion, or any of the other methods to which we're all exposed and now have no defense against.