Unfortunately these portals don't offers such a functionality as closing off rooms. However, we can advise you some way around to avoid unwelcome bookings from this portals for selected period.
We suggest you to set prices for this rooms on ridiculously high level (e.g. 1000% of the normal price). In order to do it please create a new rate and using 'Schedule Pricing' set up this ultra high prices for selected period. Then please go to to 'Online Portals' and sync with portals using this rate with ultra high schedule pricing.