[SMALL ISSUE]

When you construct a PotionEffect
new PotionEffect(PotionEffectType.EFFECT HERE, TICKS, AMPLIFIER);

You get a problem with the Amplifier.
Level II seems to be 1, and level III seems to be 2 and so on.
I know you are always tought computers starts with the number 0, but Minecraft doesn't.

TEMPORARY WORKAROUND FOR API USERS:
Pretty self explaintory. Pass in the number - 1 in the constructor.

FOR THE SPIGOT TEAM:
All you guys on Spigot would need to do is to add a -1 in the constructor I guess!
And that would save people from doing silly misstakes