I'm sure there are a million and a half different versions of this problem posted on here but I've scoured thread to thread and nothing's worked. I'm hoping to get a suggestion I haven't already tried.
The situation: Just last night I was running well over 100fps no matter where I was. The most lag intensive thing I was by was a build I'm working on which brought me down to 120fps minimum if I was looking right at it. (If I stared up at the sky I ran a max of ~800fps) I even averaged ~380fps in the nether. So it was quite the surprise to me when I logged on today and I maxed 18fps while looking at my build, and a max of 80 if I looked at the sky. Despite what settings I change I've also started to get a lot of lag spikes that bring me down to 5 frames for a second.
What I've tried/info: I have optifine, I had everything at max settings originally but even turning everything to its fastest settings didn't help my frames in the slightest. Nothing is taking up much of the disk or my cpu, minecraft is already set as a priority in my task manager. I've tried restarting the game, my computer, and my video settings. No change. All my drivers are up to date. Smooth fps is turned off, I've tried messing with the fps cap. Nothing. I set the JVM Argument to 6G, didn't change anything. Now, I have narrowed the issue down to it being something to do with optifine. If I launch vanilla 1.14.4 it runs amazingly, same great frames I saw the night before while using all max settings with optifine.
What's really throwing me off is not just that optifine is suddenly ruining my frames even though it wasn't yesterday, what's tripping me up here is that I reset all the videosettings (I just hit the button to reset everything so no, I didn't miss a setting) and my frames are STILL taking a dump. Which would lead me to believe that it's optifine itself that's the issue and not any of the settings. But then I have to wonder why it's causing issues now but wasn't before.
The one thing I didn't try was reinstalling optifine and that worked, so, resolved. Sorry bout that.