The loved-up couple are said to have been arguing and bickering in the Spanish resort over cheating claims, and things are so bad that Harry is flying home to the UK early.
Just days before they left for Marbs, Bobby spoke about how well his relationship with Harry was going and even insisted that they will beat the TOWIE curse of broken hearts and failed romances.
However, a source tells us: "Things are looking a bit rocky for Bobby and Harry, as they've been rowing a lot in Marbella.
"Harry is even flying home early, which has left everyone wondering whether they are even still a couple."
Another insider adds: "The guys have been arguing in Marbs following some cheating allegations. Whether true or not, the claims have stirred things up in the relationship - and not for the better."
Bobby and Harry - or Barry as they are also affectionately known - started dating almost seven months ago and things seemed to be going well for the couple.
Although he had previously appeared on TOWIE, leaving in early 2012, Harry had never starred alongside Bobby on the ITV2 reality show and they had met through friends.
However, Harry is now returning to TOWIE and flew out to Marbella with Bobby last week to film the first scenes for series 12.
Before jetting off, Bobby had told Reveal that, although apprehensive about being in front of the cameras with a boyfriend, he was looking forward to filming with Harry.
He said: "I'm looking forward to getting out to Marbs with Harry. I'm intrigued to see what it's like to film with him, as we've never been in TOWIE at the same time. It will be nice to film with him, but it's a bit weird as I've never had a boyfriend on the show before!"
Bobby added: "I am a little bit worried about the drama – I think it's kind of clear that TOWIE is cursed when it comes to relationships – but I'm hoping, praying and touching wood that the gays can beat the curse!"
Hang in there, guys, as we think you make a fabulous couple. Besides, who else could carry off matching asymmetrical thongs?