about the three sannin fight, jiraiya was drugged (30 percent of his power) and oro had no hands (half of his power or even less) these two were handicapped. tsunade cannot win against any of the two sannins in a 1on1 fight (she is a medic for the love of god), if oro had his hands back then, he would have eaten her (no brainer). this is turning to an oro vs tsuande POINTLESS thread (who is stronger is obvious)
Just for the sake of clarification. Tsunade was at a handicap as well. When she fought in the battle she was no longer a shinobi and hadn't been apparently since Dan died. Thus, she was extremely out of practice, by almost 30 years.
In addition, it is a manga fact that she was also unrested.
She also fought a battle before engaging in the sannin battle
and opted to take Orochimaru's sword attacks and heal from them which means depleted chakra levels
And finally, due to the fact that she was drunk the night before, it's likely she had a hangover