So I use feather client, and I suspect it has something to do with that, as it has its potion display mod, but I prefer this one. Whenever I splash potions, the background for it doesn't show up, and it's just transparent, it's not the biggest deal but I did a test fight and couldn't tell that my potion status had run out.

What exact other mods do you have installed? Can you determine which one it is that causes this problem?

If you want this fixed I need your help to pinpoint the exact mod that is problematic. I suggest two methods. Either you do "divide and conquer", disabling half of the mods and checking if the problem still occurs. If so, you know it is one of the remaining enabled half, otherwise it was one of those that you turned off.

Then you repeat the process with the half of the mods you know contain the problematic mod -- disable half of those as well, etc. In the end, you will be left with a single mod, that if you enable it, the problem appears, and if you disable it, the problem is gone.

Another way is to use a bit of common sense and shortcut the process. If you have reason to believe a certain set of mods are not likely to be causing this, start by disabling those and verify that the problem still occurs. If you do this cleverly, you can probably get to a short list of possible mods much faster.

These are all the other mods I use.

Alright, I have to go somewhere, will do this when I get back and will let you know the result.