jmc

Because there was an odd number of scores, $91$ must be the middle score. Since there are two scores above $91$ and $94$ appears the most frequent (so at least twice) and $94>91$, $94$ appears twice. Also, the sum of the five numbers is $90\times 5=450$. Thus, the sum of the lowest two scores is $450-91-94-94=\boxed{171}$.