I flushed my auto tranny's fluid by disconnecting the supply line to the cooler, emptying out about 2 quarts, and adding 2 quarts from the dip stick until I saw new fluid come out. I checked the dip stick a few days later, it's leveled off but I noticed there are streaks of the old fluid that is not mixing in with the new fluid (on the dip stick). My tranny shifted good for those few days, and didn't hold onto 3rd gear for too long, but since I noticed this, it's having the hard shifts again and holding 3rd gear.

Do I do another flush?