I don't like the weights, not because they are lead, but they can squash the plants stalks, but they are safe (the ones you buy at the fish shop), my mother used them for years, and when I inherited her tanks I foung about a hundred of them mixed into her gravel, I removed all the ones I found, but I still find them every so often.
but in one of those tanks I have a 15 year old talking catfish, so I guess they must be safe.