Why has minecraft started running slow?

I have had my computer for about a month now, and I downloaded Minecraft. It ran at a stable 60fps-100fps. Recently I have been getting under 30fps. Why has this happened? I don't recall downloading anything besides a few texture packs (which I am not even using). WHat can I do to fix this?

Specs:

Gpu: Amd radeon r7 240
Cpu: AMD FX 4300 Quad-core (3.8ghz)
RAM: 2x4 DDR3
Motherboard: Gigabyte GA-78LMT-USB3
Windows 10 Home 64-bit

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