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Hey, just recently I saw my two turtles extending their arms at one another, almost locking hands, sometimes they grab each other's heads.

I usually never even see them face each other so this seems strange. Can't tell if it's affection or aggression... They get along well in the tank otherwise.

Honestly I don't know the genders of my turtles which is why I named them genderless names. I still need to upload some pictures

That fluttering can be both affection or aggression, as I understand it. Watch out for any meaner behavior like nipping and whatnot. If they start doing that you will have to separate them, so be prepared for that possibility.

If both are doing it, it is likely aggression/territorial. Keep an eye on it and if it escalates to chasing or biting, you need to separate them.

If they are still very young, say less then a year old, they may just be playing. It's all an instinctive game for youngsters, they probably don't know why they are doing it, it just feels good. But if they are older, and both the same gender, it could be a territorial issue. I'm sorta going thru to same thing with 2 girls and a male and lately it seems to be escalating to the point where I had to move the male to a new habitat for fear he may get hurt by one of the females.
Those who are thinking of getting 2 (or more) turts in one tank need to take into consideration the time may come when the "playing" could turn into something else altogether, and one turt (or both) could get seriously hurt to the point that they may need serious medical attention ($).
Here's a thread going about it on now:
http://www.redearslider.com/forum/viewtopic.php?t=10669

They are just over a year old grey goose. I've watched them a lot, they never really bother each other, and I haven't seen them grab each others arms in a few days now. They constantly climb ontop of each other to get closer to the heatlamp, but I think they take turns and don't mind that.

The only time they are really competitive is when the food gets dropped in, but they never get physical.

So far they're getting along fine

If it's during feeding, you might consider taking the more aggressive turtle out during feeding time and feed him in a separate container while you feed the submissive turt in the tank.