i have them set to 0 in the config for the default stack size but i can still stack them and i dont what them to stack.  

here is my config

{
"Settings": {
"CategoryDefaultStack": {
"Ammunition": 256,
"Attire": 0,
"Common": 0,
"Component": 100,
"Construction": 0,
"Food": 100,
"Items": 0,
"Medical": 15,
"Misc": 0,
"Resources": 25000,
"Tools": 0,
"Traps": 0,
"Weapon": 0
},
"DefaultStack": 0,
"StackHealthItems": true
}
}

There are two ways  to do it and ensure that it is what you want, The first is: unload the plugin , go to your data folder and set each individual item to 1 that you dont want to stack , save and then reload plugin,
The other is to use in chat or console with the plugin running:   /stackall 1and you should get confirmation , *Then use /stack metal.refined 25000 and do the same for your other resources and what other items you want more of, here is the item list link.
https://www.corrosionhour.com/rust-item-list/