I just started getting these within the past three days. I had a TON of baby snails start showing up in the tank as well, but these to me are more like flat drops of white. Looks exactly like your pic.
I just used a magfloat to scrape them off, but to be honest they are super hard to get off, and leave a small "spot" where I can't completely get it off.
When you say baby snails showed up did you have eggs in your tank that hatched? If not you might want to do a little research on pyramid snails.