It's more like 5-10 points each. I wouldn't worry about it if you're already at 780. After a few months it will be like it never happened. Your score might even go up.

However, don't apply over three months. Apply all on the same day, within minutes if possible. You don't want Application A to show up when you fille Application B, and for both A and B to show up when you file Application C. If you do them at once, it will look to all of them like this is your one and only card you are applying for.