overnight change in water condition

Question
Virtually overnight my tropical fish tank changed to a dirty pond water. The nitrate level went to 40ppm (deep orange) and the Nitrite level had a reading of 5 ppm (deep purple. Ammonia was ok and Ph level was 6.0. I don't have a spare tank to put my fish in and aquarium supplies are available 200Kms away.
I have changed 1/3 of water of a 15gal tank and I have put on another filter so I now have 2 filters running but it will still take time to reach the required levels. Is there anything I can do in the meantime to assist the process?
I may have inadvertently started this process by trying to collect small snails off the bottom of the tank and disturbing the the gravel.

Answer
Ken,
cut back on the feeding, and only change a gal or two of water at a time unless you are in a critical situation.
You could use "Cycle" to assist if you can get some..if not, I am going to guess this is an older tank as the PH is low, unless your water is naturally that low..keep the two filters running and only change one at a time that way you always have a charged filter biologically keep the tank stable.
watch the fish, if they are doing ok, then its ok..if they are at the top, clamped fins, or hugging the bottom more drastic measures would be necessary...ie, major water change, remove the fish, put them in a bucket or whatever will hold them, clean the top 1/3 of the gravel and change 10 gals....then re-aclimate the fish...only do this if necessary...
Good luck...