Ammonia is high. Your beneficial bacteria colonies might have crashed for whatever reason.
My recommendations:
*remove about 30%-40% of the water
*rinse out filter units
*clean the filter pad of one of the filter unit (with tank water, not tap water) and put a brand new filter pad of the other unit.
*you should do a 30% water change every day for the next week and check ammonia before the water change.
*if ammonia level stays .5ppm or less you can do less water changes
*in about 3weeks, put a brand new filter pad in the other filter unit