Yes, bromine can't be stabilized against sunlight . . . and the presence of bromide ions (used up bromine) prevents chlorine from being stabilized.

Drain as much as you can safely drain, and then refill. Bromide ions, in the absence of dimethyl hydantoin (DMH), will apparently be converted eventually to an inactive form, bromate. But the DMH apparently prevents this. See http://pool9.net/bromine/

If you used more than a few pounds of bromine, you should drain as far as you can, refill to 3x that depth (6" => 18") and drain again before final filling.

Sorry!