Three men died over the Christmas period in Ipswich and Rendlesham and their deaths were initially all being connected to the PMMA form of ecstasy.
In March, Adrian Lubecki, 19, of St Matthew's Street, Ipswich was jailed for supplying drugs.
A 21-year-old has been given a caution for possessing amphetamines, while a 26-year-old faces no further action.
Suffolk Police arrested those two men in January and they had been released on police bail since then.
Lubecki, originally from Lithuania, was jailed for supplying PMMA to Justas Ropas, 22, of Bramford Lane, Ipswich.
Mr Ropas, also from Lithuania, died on Christmas Eve after taking one-and-a-half PMMA tablets, which were embossed with the Superman "S" logo.
Lubecki had stashed 461 PMMA Superman tablets and 49 MDMA tablets, featuring a snail logo, at a property on Norwich Road in the town, which he told police about after his arrest.
Suffolk Police were still investigating two other deaths on New Year's Day.
The death of Gediminas Kulokas, 24, who was found at Provan Court, Ipswich, was being linked to the "Superman" tablets.
The death of John Hocking, 20, in Rendlesham was not being linked to the other two deaths, police said.
Inquests into all three deaths have yet to be completed.
Two men, arrested as part of an inquiry into "Superman" drugs deaths in Suffolk, will not face court action.