Drop in fps after applying different patches/mods

hi just a question why does my game suddenly has a drop in fps after installing scoreboards, courts, jerseys and the like? The normal fps for my system is a stable 60 fps but when i apply for example the tnt scoreboard my fps drops to 40-50 fps. Here is my specs:Intel i3-3210 3.2ghz, gigabyte h61m-ds2 3.0, 4gb ddr3, amd radeon hd 5500 series. Thank You

They are more detailed which leads to heavier load for your pc.
Question is, if you don't get spikes under 30 fps why would you care?