Female guppy

[Cmlee]

IMG_20160816_220912.jpg

Was pregnant , now becomes a lump at the back and skinny

Any idea whay happened?

[Guppendler]

The picture is not sharp, but the lump you're referring to is not at the back but at the anus.
Your female guppy is suffering from prolapsed uterus, which is a symptom that could be very likely caused by hexamita (wasting disease). Fish with compromised immune system would likely to succumb to this disease.
You may try treating the female guppy with Epsom salt but in this case the protruding flesh seems very far out and is unlikely to retract back to the body.
Such fish would not usually live very long.

[Cmlee]

It was very healthy and lively , then suddenly become like this. Other guppy is OK. Guupies seems to die any time even with regular water changes. Maybe I should stop keeping guppies ?