Sulfur only works as a preventative. If a pine already has fungus, (even powdery mildew) it needs to be treated with another product.
But I don't think the fungus is what caused the problem. If I had to guess, your pines are suffering from freeze damage and/or were sitting in a saturated condition for too long. Parts of the tree died, and the fungus arrived on the scene after the buds/needles were already dead. I don't know what kind of weather you experienced, but freeze damage is much more likely when there are dramatic swings in temperature, particularly if there is high wind. At what point did you notice the needles browning? They should have stayed green throughout the winter...
Pulling the trees out, giving them fresh air, sun and good drainage, will hopefully allow them to recover. I don't know that treating them with a product will make a difference at this point, but if you want, you could spray them with neem oil, which I use regularly on my black pines. Just don't use the oil if you applied sulfur in the last 30 days.
