Minecraft FPS drop for no reason?

So yesterday my minecraft was running really smooth. I was getting 90-120fps with 12 render distance and fast graphics. However, when I went on tonight, I was getting terrible lag, so I went to check my minecraft FPS. I was getting around 50-30fps which is odd because I usually no less than 50. I tried turning down my render distance, turning smooth lighting all the way off, but nothing seemed to work despite my best efforts. Please help me find the problem and Aldo if you can, give me a solution.

If your using the new launcher then click on edit profile and near the bottom where it says "JVM arguments" there you can give minecraft more ram. Give mineccraft 50% of your ram it is not recommended to go higher.

Eg. Computer has 4GB of RAM, the box would say: -Xmx2G

Your java/Minecraft is running out of memory which is causing lag spikes. Go to launcher for minecraft edit profile and at bottom it should say java memory put atleast 2gb of ram. That shold help alot