I think this is a problem with two plugins working together. Basically, the health, mana, and tp bars can be drawn every second. When you increase the number of characters on screen, this workload increases.
Even if you remove a character from the screen, if that character's data persists, the system can continue loading and processing that information. I made an update focused on this; just update the v4.5 file. This fix changes the bar update criteria and correctly clears the data when characters are removed. I hope this resolves the FPS drop.
Could you please download the file again and test it?