If a monster has had its ATK or DEF changed through its own effect, and later on Skill Drain is activated, do the monster's stats revert to normal?

Example 1: Zombyra the Dark has attacked and destroyed 2 monsters, meaning his ATK is now 1700. Then Skill Drain is activated. Does Zombyra the Dark's ATK revert to 2100, or does it remain at 1700?

Example 2: Raging Flame Sprite has successfully attacked directly twice, meaning her ATK is now 2100. Then Skill Drain is activated. See above question.

Skill Drain will negate the resoultion of effects of all face up monsters on the field; so if they have an effect that alters their atk/def it will be negated and the card will revert to its original values.

Zombyra will go to 2100.

RFS will go to 100.