Great question, something I get asked about a lot…The first thing I’d recommend to to check out the two “right hand technique” videos on the site, that should give you some good insights.
One thing that comes to mind is that you may not be striking the string properly on the low strings. Your fingerpicks should strike the strings almost perpendicular to the string. A common problem is that a player may be twisting his had to reach the low strings, and then the pick strikes the string at too much of an angle, and you get much less tone and volume. The pick scrapes across the string instead of punching directly across in a perpendicular fashion. Try playing the section your having trouble with VERY SLOWLY and look at your right hand technique as you play. See if you can spot the problem visually and make the correction.
LMK how it goes!