Due to the confirmation that at least one of the females is gravid, I have removed one girl turtle to a separate soiled area.
Did you remove the one that is gravid, or are you identifying by process of elimination?
If the non-gravid one gets placed in dirt, she will stress. Likewise, if the gravid one is left in the tank, she will stress.
If you noticed the eggs around the same time each evening, maybe keep your eyes peeled for which female is going psycho around that time - yeah, gravid is the official term, but "psycho" seems to explain it better to me.
It took me a long time to figure this gravid stuff out (like yesterday), but finally realized that it does in fact happen around the same time each day / night.
The time to move the gal to a nest is when she starts showing signs of wanting to get those eggs out (i.e., acting psycho). It's not necessary to "banish" her to dirt if she is acting calm, behavior is unremarkable, she is eating normally etc.
Basically, if her behavior leaves you wondering, "what the heck is up with her?" then it may be time to watch closer for frantic swimming, escape attempts, etc. ...actually, since you have more than one female, odds are the little "egg-layer's" behavior will stand above the crowd.
At that point put her in a nest until she starts walking around and acting like normal (I just learned this yesterday)
Look for eggs afterwards (gently brush away the dirt) - if there are eggs, then she is the culprit
If no eggs, well...check back and we can move on from there

Of course, you could be the lucky recipient of two gravid females at once...same behavior applies.
Best wishes!