50 Cent raised the stakes in his beef with 3 rap heavyweights -- publicly insinuating Diddy, Rick Ross and former record exec Steve Stoute are gay together ... but he backed down minutes later.

The shots were fired Sunday -- Fiddy posted the 2 pics on Instagram, one showing a pink-shirted Stoute embracing a pink-shirted Diddy. The other shows Diddy and Rick Ross from an angle that makes it look like they're kissing.

Underneath, 50 wrote the caption, "I ain't saying nothing, but something ain't right. Lmao." He yanked the pics down a short time later.

The photos were the latest in 50's ongoing feuds with the rap titans -- Stoute recently appeared in a VH1 documentary about hip hop, in which he called 50 a has-been. 50's been feuding with Rick Ross and Diddy for years.

As for why he pulled the post ... 50 probably thought twice about starting a nuclear war.