It does it to me on any version.
I am trying to play modded through minecraft forge 1.12.2 to be more exact. And anything I try won't change it. I don't know what to do can you please help. Even if I am not trying to use mods and just go on regular vanilla it still only has 1GB of ram to it. I have a total of 16 gigs of ram, if you need to know.
Had to cut video of what I mean in 2 gyazos (The first one shows that I have 4G in the JVM arguments and the second one shows that it is locked to 1GB)
But, you mark this error as 1.14.3 error, and it isn't a problem from 1.14.3 pre-release 3, maybe it's a launcher error. I mean, you are trying to load Minecraft 1.12.2 with forge. It isn't a 1.14.3 pre-release 3 fault.