Not that you aren't experiencing a bug, but for most people just using the potion during any fight works.

Do you play using mods, is there a conflict causing a problem?

Actually i m on a new playthrough that i had to do that quest just a few moments ago. Worked just fine.

And you dont have to kill them with the potion, you just have to hit them with thunderstorm.

However if you encounter extremelly weak enemies, the kind that dies in 1 hit, it may not count for quest progress. (sometimes happens)

Side Note:
If you have SQL mods, they can interfere with the quest progress, as most of them are very outdated.

Originally posted by JHarlequin:

Not that you aren't experiencing a bug, but for most people just using the potion during any fight works.

Do you play using mods, is there a conflict causing a problem?

yep it was the mods, thanks for the help

Originally posted by OtherWise:

Actually i m on a new playthrough that i had to do that quest just a few moments ago. Worked just fine.

And you dont have to kill them with the potion, you just have to hit them with thunderstorm.

However if you encounter extremelly weak enemies, the kind that dies in 1 hit, it may not count for quest progress. (sometimes happens)

Side Note:
If you have SQL mods, they can interfere with the quest progress, as most of them are very outdated.

yep it was the mod, thanks for the help

which mod was it, if i may ask?
In case i may get the desire to run it in the future (and heads up that its problematic helps)

Originally posted by OtherWise:

which mod was it, if i may ask?
In case i may get the desire to run it in the future (and heads up that its problematic helps)

not entirely sure, i removed all potion related mods that changes numeric value: stack size, longer buffs, etc

Works fine here. I have no issues doing that quest