Unwanted "Documents and data" slowly taking my phone's memory
That's cache. You can delete cache in Twitter and Facebook by logging out, then log back in. Or delete the app, then reinstall. Some apps like TapaTalk have a built in delete cache option.
You can delete some phone cache with the app, Battery Doctor.
That's not much on your Twitter. I've seen Facebook go up to 1 gb.
It's storage space. Memory is RAM.