Wow that's really unlucky then.
The probability of getting all 3 Stars from a single 10+1 pull is ~0.57%.
The probability of getting one 6 Star from a single 10+1 pull is ~5.23%.
(This was all done assuming rate for 3 Star = 63.5% and rate for 6 star for 6 Star = 0.5%).
Then again, I don't do that Gacha anymore. I just do the Event Gacha with better rates regardless of if I like the Event Girls.