Hi James. In a fixed run I always advise at least 4 square metres per bird, or 40 square feet. That can be reduced slightly with more placid breeds and it helps a lot if there is a large perch in the run which is big enough for all of them. We used to have just over one square metre per bird in runs that were moved regularly but also the birds free ranged in the afternoons. They got really stressed waiting to get out as 1 square metre, or 10 square feet, is far too small. Just letting them out for 10 minutes makes a huge difference in my experience.
You only have 32 square feet for 4 birds. I would quadruple that space at least. In small runs you get stressed birds getting ill and also bullying and feather pecking with boredom. As Mentalmilly said, when the weather changes and they have no grass, just mud, the current picture of happiness will change.