>>45795540I'm sure u did this already, but just to make sure, check to see if you have enough ram allocated in MultiMC settings. Try for 6gb if you can. Can also try these JVM arguments:
-XX:+UseParallelGC -XX:ParallelGCThreads=3 -XX:MaxGCPauseMillis=3 -Xmn256M -Dfml.ignoreInvalidMinecraftCertificates=true -Dfml.ignorePatchDiscrepancies=true