Sunbirds return to nest after abandoning chick

Hi

I read the other post re sunbird nesting frequency but didn't want to hijack that post. For the first time I have a pair of olive backed sunbirds who nested on a string I put up for that purpose outside my kitchen window. She would perch on the window often & look at me & was tolerant of me in the yard - I made sure I stayed well away from the nest. A single chick hatched & all was well for about 8 days until last Monday when the female wasn't at the nest in the morning as usual. I thought she had set out early to get food. I didn't want to interfere & went to work quite early. I came home in the dark & didn't want to shine a light on the nest to check if she was there. The next morning still no sign of her & the nest was still. They appeared to have abandoned the nest although I still heard the pair calling, without alarm, & saw the female feeding in my backyard one morning but not near the nest. On the following Friday (last night) there was an unseasonal storm with lots of rain & wind. This morning the male & female returned to the nest & the male appeared to try & either feed the dead chick or remove it from the nest. They flew away quite quickly after this. I'm unsure why they would abandon the chick to return days later?  Do they want to remove the dead chick & reuse the nest? Should I leave the dead chick in the nest? I really love this pair of beautiful birds but don't want to interfere or do the wrong thing. Any advice welcome. Thanks, Lily