The Hammers, who lost 2-1 to Premier League champions Manchester City on Sunday, went into the recent international break on a high after beating Liverpool and had been free-scoring in the early weeks of the season.
But have slowed down and Michail Antonio, the club’s only senior striker, has just one goal in his last nine West Ham appearances.
Asked if he was concerned by the form of his forwards, Moyes said: "Yes I am, I’ve told them.
"I think that we need to be better in that area. We’ve had opportunities and when you get to the top end you have to have forwards who individually can beat players, make goals and create chances and be clean with the chances, we haven’t been in recent games.
"I go back to Europe, we won in midweek but I thought our attacking play could have been much cleaner with our chances."
Aaron Cresswell, a key part of West Ham’s attacking play with his delivery from set pieces, was forced off with a back problem after colliding with the post in the second half when blocking a City attack.
"Aaron is OK, his back is stiff," said Moyes.
"It went into the goalpost and he felt when he lifted his leg up there was a spasm really. First of all I got the message to say he was okay and then 20 seconds later I got told no he can’t move his leg so that is why it all changed round at that point.”