I think it would be good to reach out to the rescue and see what they advise you to do. They may be able to take them back from you and work on their bond for you, since they were so recently adopted. It does happen sometimes that a change in location can trigger an upset in the bond. Do you know how long ago they were spayed?

I wonder if something in the garden triggered them? Maybe the smell of other animals? It could have also been “too much too soon” in terms of the new space.

If the rescue can’t do it for you, the best thing would be to work on re-bonding them. You can read about the process here: https://binkybunny.com/infocategory/bonding/

Basically you would do dating sessions in neutral territory while preventing fighting to allow them to reestablish their dominance hierarchy safely.

I’m sorry to hear that you are having these difficulties– it’s fortunate that no injuries have occurred outside fluff-loss.

It is possible that the rabbits were not properly bonded or the bond they had was not very secure. Transitioning to a new environment can tense a bond, but we typically do not see it dissolve to fights-through-a-pen-wall level. While unfortunate, you likely need to go through re-bonding the rabbits. If they indeed were bonded before, it hopefully will not take as long to progress through the steps. See here for a bonding overview: https://binkybunny.com/infocategory/bonding/  .. essentially, you want the rabbits to establish comfort/hierarchy in a neutral space, and then progress to semi-neutral (where both rabbits have been before/the shared space). During bonding, you do need to house them separately. You should have a gap between their spaces so no nipping can occur through the pen wall.

As a side note– is one of the rabbit’s molting? This can potentially explain fur fluff everywhere, though unlikely based on your described context.