Breast augmentation and refraining from communion are not sins.
You have NO business asking someone why they aren’t going to communion on a particular Sunday or any day. The Church requires once per year, during Easter time. The person may have eaten something right before mass and not maintained the fast, they may be conscious of a sin they need to confess, they may find that they are better able to give proper devotion to the Eucharist when they do not receive every time. IT IS NOT YOUR BUSINESS. They are not doing anything wrong. You, however, are being VERY rude, nosy, and yes gossipy.
Regarding breast augmentation, there can be good reasons and not so good reasons for such an operation. AGAIN, not inherently sinful, and NOT your business. And certainly not your business to tell other people about it.
If you see someone who is ACTUALLY committing a sin and you meet ALL the criteria that should be in place for fraternal correction (see here:
newadvent.org/cathen/04394a.htm) THEN you can PRIVATELY talk to them. And you need to do so out of charity, love for them, not with glee that you are lording it over them.
You cannot and should not spread around to others whatever it is you have discussed privately. That is indeed gossip.