Milky white tends to indicate a moisture issue. 2.5 minutes of stirring is pretty fast but as long as it was clear with no streaks you should be OK, presuming it cured properly.
The moisture could be from humidity, the wrong type of mold release (if you se any) or residual moisture from whatever you are putting in your tubes for casting over.
If persistent, the first thing I would try is preheating the mold, even with the tube and all in it. You should start this as a new thread to get better input.