Looks good, but perhaps try using switch statements in your code, that would boost performance.

This is a good plugin but i want to add something to remove the effect and change the timer between 2 number . if you do this i will give 5 stars

The plugin works 100% as promised, however I feel like you should add an enable and disable command for the random potion effect thing, it would make it a lot more useful and convenient. Was gonna leave 3 stars but you said you're gonna add random duration so ill bump it up to 4.