Okay my teacher has this exercise so that I would strengthen my 4th and 5th fingers. She would press C, D, E, F, and G with each fingers placed respectively on both hands. After it, she would play one note for four times but the other four notes are still pressed down. I'm still working on it. But any exercises where i could still strengthen my weakest fingers? Yeah I know scales. But sometimes my fingers would collapse or bend inwardly especially the fourth fingers. What should I do?