Would you buy that company today at the current price? If so, leave it there. If you would NOT buy it today, there is a strong argument for re balancing.
If you are lucky here, you will have it all in a taxable account, could sell, buy $10k of VTI, and claim a $15k loss on your taxes which may take a bit of the sting away! If it's in a retirement account no such luck, but $10k into VTI right now will be a good idea for the future.