Tank Emergency!!

[Carmen]

Help PLEASE!!! Ofcourse I am leaving on holidays for 2 weeks on Sunday and my tank has started to show mega nitrates!!!!! First time anything has ever been outa whack and it's right before I leave!!!
So I tested on Tues and it showed Nitrates about 5(possibly 10 as I cannot tell the difference on my tests). Did a larger than normal WC of 5 Gallons (it's a 27G bowfront). Retested Thursday and said the same did another almost 5G WC and cleaned the canister filter out completely as I figured perhaps that was the source as it had accumulated alot of debris. Kept the rubble submerged most of the time only out of water to transfer containers to clean it. Changed the carbon, cleaned all powerheads, siphoned off rocks in tank of any detrius.
Rechecke nitrates tonight and shows Nitrates of 20!!!
NO NOTHING has died! NOTHING! Corals look okay with a litle less perkiness to some. Fish are fine and eating so far.
HELP!!!!! Now what! I have no salt water mixed right now will mix some up but what am I going to do? Anyone PLEASE!!!
And there is no option not to go on holidays so what do I have the sitter do?
Carmen