Nathan Allen, 21, died after being shot in the chest in Ludwick Mews, New Cross, on 3 May.
Two men aged 19 and one aged 18 were arrested on Wednesday and bailed. A youth aged 17 was held on Saturday.
Mr Allen, who lived in nearby Desmond Street and was also known as Mace, died at the scene of the shooting.
Father-of-one Nathan Williams, 24, was shot dead in the same street as he sat in his VW Golf in the early hours of 28 July last year.
No-one has been charged with the killing and a 25-year-old man questioned by detectives was released from bail last Tuesday.
Police faced a third murder in Ludwick Mews four years ago when Jason Gayle-Bent, 29, was stabbed to death outside his home.