This was an issue on 0.30 or one of the other early hotfixes, but should have been fixed in 0.30.1G or F. The cause for it was an error with missing visual effects for the potions.
If you are on 0.30.1G and still get these, then I'm guessing you had an error on it but hit 'ignore'. Now the error simply doesn't show up, but nothing happens nonetheless.
Assuming this is the case and you had some errors during combat. You'd have to remove the persistent data from appdata and the save folder inside the game. That would 'reshow' you the error so I could fix it. I'd recommend backing up that persistent save file though. It contains gallery unlocks and other stuff.