Option 1: You could do an "early decision" round, and a regular round. If the early round is very early (february?), and the regular round at the current schedule, the other seed firms would have to really come out into the open to pre-empt their decision date before early decision.

Option 2: You could move your schedule early up - to have your interviews and decisions wrapped up by March 1 - and give the startups a whole month to decide (Just to signal your integrity). Then if the other seed firms gave just 48 hour exploding notices that would really sit in stark contrast.

You want to force them to signal their bad integrity out and clear in the open. Right now they're able to be dirty in the closet. If you force them to come right out, especially if your actions are diametrically opposite, you win.