Strange ammonia spike in 29 Gallon

[TropicalDares]

hey everyone, the water in one of my tanks has become so cloudy over the past night that even the fish swimming look like a blurr so the first things i done this morning was a water test and then a water change after i figured out the ammonia was btwn 4.0-8.0 ppm, and the nitrate was around 20 ppm however there was no sign of nitrite

- i haven't added anything into the tank in the past 3 weeks

- i also had a dead pleco this morning

- yesterday the tank was crystal clear

- i dont trust everyone in the house, (could something have been poured in to cause this?)

the stock is 2 3" yellow labs
1 red zebra
and 1 of the albino looking ones

all are around 3-4"

 

[Neophyte]

How long has the tank been setup, has the filter been cycled and what are you using for filtration?

 

[TropicalDares]

it has been setup for about 6 months now, the filter is an aquaclear 70

 

[Neophyte]

Have you cleaned your filters lately? If you cleaned them too well or replaced too much media that can cause a tank to uncycle. Has power gone out for any length of time or could you have done a water change without adding dechlorinator?