Guppy fish lump

[Sanyod]

Hello All experts,

Please have a look at my guppy and suggest if you find anything wrong. I think she is pregnant and I see a lump on her sides. Do you think it's normal or some kind of disease?
Sorry for the photo quality

 

[jonny-5]

What are the water parameters like?
How big is the tank?
What else is in the tank?

 

[Sanyod]

My tank is small 50L & have around 13 small guppies. Tank is 1 month old.
We checked the water parameters, Nitrate levels(No2,NO3) were a big high, water hardness is always high. We changed 30% water thrice till now