I realise this is attributed to deplenished glycogen stores and water weight, however I am following the V-Diet pretty much exactly and I feel as though muscle loss is occurring.
Would it be a good idea to carb up on weekends, to replenish glycogen stores, or if I follow the diet strictly will the fullness and size of my muscles return once I am back on a regular carbohydrate supplemented diet?
Thanks in advance 
If you carb up on the weekends during the vdiet, then it isnāt the V-Diet.
You probably arenāt losing muscle mass, you are taking in adequate protein while hopefully still providing a strong training stimulus; that should be enough to maintain your muscle mass. What is likely happening is that you are very glycogen depleted, but you know this. When you are glycogen depleted you will not be able to function optimally. You will feel week and fatigue quickly, this is normal.
The muscle fullness will return when you transition off of the diet and eat more carbs.
Stay the course, I doubt you will regret it.
A side note, this could be a rationalization to break the diet. Bear down and finish it.