[ As for replacing the rest of the rocker arms, I'm leaning toward leaving the good ones alone. It appears the ones that broke didn't fail on their own ] I agree, after a good look at your pictures it seems you have a burn out problem on #1 causing the valves to stick which in turn broke the rockers, the burnout is noted by the excess carbon on the head also burning of the head between the spark plug and valve, also noted the larger valve is seated well into its recess and the smaller valve is sitting proud with a fine gap which would cause a rich mixture hence the burn out, i would recomend all valves be re-seated (ground in) and replace #1 valves and guides then have the engine set up properly so it dosnt happen again (which it will if you just put the head back on without a proper tune up and good luck
1989 e34 520i se, red, mint condition (original)
pro mechanic "all cars"