Please help me to solve the lack of thrust

At the moment it is possible to fly with a weight of 9 kg, but you need to fly with a weight of 12 kg.
I’m using a 5408 310KV motor and 1855 props.

I want to increase the thrust without changing the motor.

Is it possible to increase the pitch of the prop or use a 3 leaf propeller?
(Only 18 inch length props are available.)

go to calculate possibilities.

I made a payment and signed up, but the signup was completed and I only received a receipt
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Contact their support, they will surely help.

Thank you.
I changed the pitch of the motor and prop.
There seems to be a problem.

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Specification of motor

You would need 6 rotors with that configuration.