The question is best asked of an experienced real estate attorney who does eminent domain cases. (Check with the Los Angeles County Bar Association for some names). As an impacted party, you sue both the City and the Owner and let them continue to point fingers (They may both be liable although under different theories) until the Court says "knock it off".
If the owner knew of the pending settlement of the eminent domain claim and said nothing during lease negotiations you have a lie by omission (a variation of fraud) that you can hang your hat on.
A truly proper answer will require someone to sit down with your stack of documents and a yellow pad and sort things out. See an Attorney, sooner rather than later.
A proper response would require a thorough investigation into the history and background of this relationship. The information provided above is just that, information, to be used as you see fit.
Most commercial leases have a clause dealing with eminent domain issues that arise during the tenancy.
You may have an action against the landlord for breach, and possibly fraud.
You should not withhold rent, at least not until you have first consulted with an attorney.
Take your lease, and any other related documents, to an attorney in your area that handles real estate cases.
Based on the limited information provided, the other answers are correct. You should immediately seek the advice of an attorney experienced with eminent domain cases. Contact the local bar association for referrals. As far as who to hold responsible, there is no way to say without first going overall of the underlying details.
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