The 28-year-old has not scored in the Premier League since January 1 and missed a number of chances in Hull's 1-1 draw with Cardiff City on Saturday
The 28-year-old forward last scored in the Premier League on January 1 for Swansea against Aston Villa, and he has yet to break his duck since making the switch to the KC Stadium in July from Sunderland on loan.
He had a hat-trick of chances to end that run against Cardiff - his best coming inside the opening 10 minutes - but Bruce is not concerned.
"Danny has to stay strong," said the Hull boss. "I just spoke to him about that. If you're a striker, you go through these spells.
"You don't lose your ability, but you have to stay strong. That's the Premier League, it's tough.
"I'm not going to single anyone out. A striker is judged on goals. He's finding it difficult but perhaps that's why he's here. He needs one to settle him down.
"Perhaps he's trying too hard because his overall game was terrific."
However, the 52-year-old did admit that his team are going to have to start converting their chances if they want to retain their Premier League status.
"I think overall [with] the chances we created we are hugely disappointed," added Bruce. "But, to be honest, we found it a bit difficult to get to that level that we've been at over the last couple of weeks with internationals being away it is never easy.
"We had two or three of [our players] halfway round the world, and they were all getting back on Friday - it was difficult for them in particular, but at this level if you don't take your chances like that. It was our Achilles heel too in the Championship last year. We should have won by three, four or five.
"It has got to be concern because we created some very good chances. At this level you don't get as many good chances as we got here so frequently. We have to improve on that.
"It is done. It is immaterial whether he (Graham) could have taken a chance or two. It doesn't make any difference. It is history."