It seems the blend modes are wrong,
they should be
normal, add, multiply, and screen. (nothing else works as far as I know)
Also seems to return a syntax error (in a blank project)
rmmz_managers.js:2030 SyntaxError: Unexpected token u in JSON at position 0
at JSON.parse (<anonymous>)
at Spriteset_Fog.createFog (GabeMZ_FogEffects.js:472)
at Spriteset_Fog.createFogList (GabeMZ_FogEffects.js:455)
at Spriteset_Fog.initialize (GabeMZ_FogEffects.js:441)
at new Spriteset_Fog (GabeMZ_FogEffects.js:432)
at Spriteset_Map.Spriteset_Base.createFogLayer (GabeMZ_FogEffects.js:536)
at Spriteset_Map.createWeather (GabeMZ_FogEffects.js:547)
at Spriteset_Map.createLowerLayer (rmmz_sprites.js:3367)
at Spriteset_Map.Spriteset_Base.initialize (rmmz_sprites.js:3124)
at Spriteset_Map.initialize (rmmz_sprites.js:3345)