Quavo bought Takeoff the bling for his 28th birthday two days ago ... this according to celebrity jeweler Elliot Eliantte. We're told each group member now has matching customized chains -- each chain has a picture of all 3 Migos and each member is the center of their own chain.

Quavo and Offset got the chain last year as birthday presents. As for Takeoff's, Quavo spent a pretty penny on it ... $350K!!!

The gift comes on the heels of rumors that the trio might have broken up ... after Offset and Quavo stopped following each other on Instagram. Takeoff, on the other hand, kept following both.

At one point, our photog asked Huncho about a possible split, but he didn't say much and instead talked about his collab with Takeoff, "Hotel Lobby". A label rep later told us, the trio was still very much together ... but they had to cancel their Governors Ball performance because of a scheduling conflict.