I would be careful about making any changes to an existing card with another bank. First of all, I'm not ever sure that that's what Citi is complaining about. Most likely they mean the credit you have with them.

Second of all, it can take them a month or so (reporting agency lags) before Citi will be able to see the change on your Chase card. By then, it's probably too late for a "reconsider" on the current app, and you'll have to wait 60 days to do a new app, by which time (unless it's extended) the 75k offer will either just be over or be almost over, depending on when Citi thinks you made this app.

Third, a change to your Chase card, even if it's to lower the credit limit, could generate a pull. (Depending on what else you've done, that may or may not be signficant.)

You didn't mention how much credit limit you can spare on your Citi Gold card, but that's likely the only place you can reduce that would help your new app that's already in process.