Puppy won’t drop the mulch

I’m getting desperate. I have a 4 mo old golden who is really good at drop it for everything except small things outside (rocks, acorns, and MULCH. Especially the mulch). She’ll drop anything that sticks out of her mouth like sticks and leaves with no problem. Her leave it is also really good, but she is still able to sneak some things that I don’t always see in time to tell her to leave it. I don’t want to constantly take things out of her mouth out of fear that she’ll learn to resource guard, but then she was pooping and throwing up mulch. I’ve tried increasing the value of the reward for dropping it to no avail. I’ve tried trading for high value stuff, but she’s not interested (which is crazy because she is so food motivated). I even tried offering a bigger better piece of mulch that I know she would end up dropping bc of its size, but nope. We’ve gone through treats, stinky freeze dried meats, turkey tendon, chicken. I’ve tried throwing something yummy up ahead for her to “find it” in hopes she’ll drop the mulch. She’s really good at “yes work” and so far it’s pulled her attention from anything and she always gets a treat. I’ve tried that too and she’ll give me her attention, but won’t drop the mulch for a treat. Ive placed some mulch along our walk and even inside to practice as much as we can and at it’s gone no where. Is there anything different I can try that someone has success with? I’m considering a muzzle.