Because the residual sugars remaining are much less, I would expect closer to what you saw for the secondary fermenting. Krausen levels are also yeast strain dependent.
All in all, I wouldn't worry. I would rely on the hydrometer more than the krausen. Also I doubt an infection, from what I've seen the further along the fermentation gets the more hostile the environment becomes and the less likely an infection becomes (given good sanitary practices).
RDWHAHB
