What is your actual question?
Are there some strokes around the filled objects that you cannot remove? Or are there no strokes at all?
Are you perhaps talking about some kind of "hairlines" which may or may not be just a screen display issue?
Also, which version of Illustrator are you using?
Sometimes it can be pretty useful to share sample .ai files, so one can take a look at the actual document.
Can you explain your problem a little more?
Are these stroked triangles or is it the preview that shows the lines?
Do you have a grey background behind those light triangles?
And what Kurt said.
Do you perhaps have the stroke on the layer itself where you are placing the light gray triangles?
We have been waiting for your response to this query. Please update the discussion if the issue is resolved or if you have any further query. We'd be happy to help