If you can smell something while grinding or sanding you probably don't have a good fit to your mask. When you have the mask on and think its adjusted properly, cover the filter intakes with your hands and breathe in. You should not detect air leaking in around the seal of the mask. The mask will suck in against your face. Same for exhaling. Cover the outlet of the mask and exhale just enough to pressurize the mask. Feel for leakage around the seal on your face.If you forcibly exhale you will leak air out from under the mask seal. So just exhale like normal and feel for leakage. Straps may need to be slightly tighter if there are leaks. Or possibly you need a bigger or smaller mask to make fitting better. I see your using a medium sized mask. Also...save yourself some money and use 3M 2091 or 2097 filters for grinding/sanding. They are far less bulky and about 1/3 the price. You will need the cartridge style filters like you have now for any chemical,fiberglass,etc. work to close out those vapors. One last thing, make sure that the rubber gasket under the filter/cartridge is in place where it attaches to the mask. Oh, and one last, last thing. When your checking the fit of your mask to yourself, move your head around side to side and up and down some to simulate your moving around while working. When your active your skin and the mask straps can push and pull some possibly affecting the seal.
Heck..just blow them out once in a while.