Hi Amy, these sentences are grammatically right and express the same meaning.

Thank you, AndyRayy. I'm gratified to know which sentences imply current topic and which sentence is habitual discussion. :D

Sentence 2 and 3 both mean the same thing as the original sentence. However, sentence 3 sounds a bit unnatural and it could be referring to something other than the present tense. Notice how sentence 1 and 2 are both in the present progressive tense, meaning that the action is currently happening (the -ing ending). Yet, sentence 3 sounds like a habitual discussion, such as something that occurs over and over. It doesn't necessarily sound like the CURRENT topic of discussion, as the other two sentences do. I think the third sentence would sound better along the lines of "Something is not relevant to the current topic of discussion."