This may be a fragment from a specific conversation, a niche piece of media, or a slight misremembering of a similar phrase. Here are a few possibilities to help you find what you're looking for:
Is it possible "matures" was intended to be another word, like "bloody matures" for "bloody amateurs" ? This is a very common phrase used to describe someone unskilled. To help me track down the specific text, could you share: bloody matures
Are you thinking of "bloody murders" (common in crime fiction or horror) or perhaps "bloody Marys" (the cocktail)? This may be a fragment from a specific
Whether you think it's from a (like British or Australian English)? a niche piece of media