It's quite possible these have rusted, but you aren't likely to know it. Look closely at the shaft of the pins; if you see little "bumps", pits, "spots" then they are likely reacting to too much humidity and there doesn't seem to be much you can do for it. Normally Clover flower head pins are so incredibly sharp and fine. I use a wool pin cushion in which the lanolin helps to keep them sharp and clean, but it doesn't seem to help the several OLD packs of these pins I had saved from my shop when it closed many years ago.
Jan in VA