Behavior in turtles.

Question
I have two 6 year old female red ear sliders.  They have been together for many years in one tank.  I have noticed yesterday that they are starting to fight with each other. They open their months and try to bite each other. One of the turtles is laying eggs, so when I see that she wants to lay the eggs I take her out
side to lay them.  I let both of them out to run around and when I put them back in their tank this is when they start going after each other.   Why would turtles start to fight after so many years.  I have not seen any bite marks on them, so I do not know if they really are biting.  Do I have to separate them now.  What ever information you can give me will help greatly.

Answer
Hello Jeani,

Oh no, after 6 years, your females are starting to fight?  Wow, I wonder why.  Could they be aggravated due to egg laying?
What is your tank setup like?  Do you use UVB lighting & a basking light too?  Are you using calcium supplementation?
I know that when they do get mature, sometimes their personalities tend to change & one may become more aggressive than another one.  It does happen, & just out of the blue for no reason at all.  
Unfortunately, if they do continue to fight, you may need to partition the tank so they cannot hurt each other.  
Are they being fed separately or do they fight over food, or can you tell?

Tracie