Yeast don't directly contribute to head retention, it's primarily the percentage of residual proteins in the beer (and lack of lipids). I can't think of any reason extra yeast or citric acid would help.
If your beers are struggling with head retention as a general rule, the correct way to combat it is to add about 5% of the total grain bill in CaraPils malt. That adds extra residual proteins that create and maintain head on a beer.
Now, the better question is why are you having trouble with head retention in the first place? As long as the beer is properly carbonated, they should be fine.
Maybe outline your process with this latest batch so we can see if anything stands out?