Minecraft not allowing 512mb of ram

Minecraft suddenly started running really badly (not sure when) so I pulled up the f3 menu and I saw that Minecraft was only getting 512mb of ram to work with, but in the bedrock edition everything ran perfectly

What I expected to happen was...:
So I searched the internet to see if anybody was having the same issue and they weren't so I decided to increase the amount of ram Minecraft could get to 2gb

What actually happened was...:
And when I started the game it still showed that Minecraft was only allowing 512mb of ram