Sour dough using unbleached all purpose flour is very wet during the preshaping My wife created her own sour dough starter. She’s been feeding it unbleached white flour. It’s doing great.
When she is making her dough during the first step she is using a recipe that calls for bread flour and whole wheat flour. However we don’t have bread flour so we are using all purpose flour. 

She’s rested the dough a few times and when she is trying to work it in the preshaping step the dough is really wet and doesn’t seem to have good surface tension. She keeps adding flour to try to dry it out. 

The dough basically is just flat on the counter...

What are we doing wrong? Do we need to adjust the recipe for the all purpose flour? Or work the dough differently? 

update
I did more research and Cook’s Illustrated suggested holding the salt temporarily for 15 minutes. Salt hinders autolyse.  They found that delaying salt hastened gluten development by an hour. 

ratios/recipe  
400 g warm water 
100 g sour dough starter 
400 g bread flour (which we don’t have) 
100 g whole wheat flour 
Rest for 60 min  
add 10g salt and 10g water  
Repeat following 3x:  
Then stretch and fold, etc.
Rest 60 min

After this the dough was as described in my post.
(I am assuming your starter is at 100% hydration, i.e., that it is half water, half flour. I am also assuming you have no/little experience in baking bread. Please correct me if wrong.)

Looking at your ratios, you have a total of 460g water (400g as water, 50g in the starter, 10g with the salt) to a total of 550g flour (including 50g from the starter). This gives you an overall hydration of just over 83%, which is definitely a wetter dough. Handling wet dough is not easy. I think there might not be anything wrong with your dough itself (although see below), and you just need to get more experience working with wetter doughs.

One thing that may make the dough wetter than the recipe assumes: both bread flour and (especially) whole wheat flour absorb more water than AP flour. Substituting AP flour for the bread flour is not going to make a huge difference, but still might make the dough wetter than is expected.

My advice: lower the hydration to somewhere in the 65%-70% range (i.e., replace the 400g water with 297g-325g). Learn to handle this dough (this might take a few trials), then start increasing the hydration.