Two weeks ago when you set up your community tank you changed the bio balance in the tank. You have 35 fish in the tank now. You are probably going through a mini cycle. Frequent water changes are needed until the balance returns. Continue testing the water frequently.
Any disruption can cause a mini-cycle and it does not have to be through Ammonia or nitrItes, although this is the most common by adding too many fish too soon.
When rhardy mentioned that you now "have 35 fish in the tank" - did you increase or decrease?
Are you removing any excess food if not eatten within a few minutes (I remove my excess after 2 hours to be honest here
)?
And yes, adding a chemical to de-toxify the nitrAtes is only masking the issue. To resolve this you will need to find out "why". HOWEVER, if this cannot be discovered prior to you leaving, for fear of loosing fish, this may be your best recource, although a poor one, to ensure that you at least have fish to come home to - Or at the least the possability...
Personally, I would do 25% PWCs every 4-6 hours until you have done 100% and re-test after a few hours.
*If you have really high concentrations of nirtAtes your fish have acclimated themsleves to it, and a sudden drop can cause a lot of stress and acclimation shock!