Need Help: I have to reset my brushes every time I switch brush

I have this strange problem where I have to reset my brushed every time I switch brushes. It's some brushes I have downloaded online and their opacity and shape keep changing and are different to the original. The only way to fix it is if I reset the tool, but then if I use a different brush and select the first one again it has changed. i have also tried resetting all the tools and tried resetting to the original photoshop brushes and then imported the custom brushed again but nothing works.