It's the warm damp weather, we've already had two 'flushes' of Blushers under the trees in our garden, much earlier than we would usually see them.
I would just leave them and enjoy them as part of the wonderful variety that Nature shows us - there may have been a little spent mushroom compost used there at sometime, or they may be 'wild' fungi but they're unlikely to do any harm to your flowers. In any case, the mushrooms are merely the fruiting body of a much larger 'plant' which is the mycelium growing underground.
