What is wrong with my platy fry?

[iwanttostayanonymous 92074]

A few months ago, my platy had fry. After a few weeks with the fry I noticed that one was smaller than the others. I tried feeding her more, worm medicine, and other medicine. Nothing seemed to work. She is very small compared to the others and does not swim around like she should. It seems very difficult for her to swim and she normally lays on my decorative cave. She also does not have a curved belly it’s kind of flat. After about 3 and a half months she had not grown at all. Now I’m getting really concerned about her and noticed today a large tumor or some sort of lump on her side. What (if anything) can I do?I feed my fish fluval Tropical Fish Flakes color enhancing and there’s the ingredients.(Size comparison)

Here is my water parameters 

Nitrate 25
Nitrite 0
Ammonia 0 
Cl2 0
Hardness 75
Alkalinity 80
Carbonate 40
pH 7.2

Edited May 8, 2023 by iwanttostayanonymous 92074

[Fish Folk]

Sorry about this. In truth, many batches and many hatches have fry with issues. I know it is hard, but probably not worth overthinking. You can choose what you want to do. I doubt you’ll see a recovery, but you can hope.

Just understand: this has happened to me hundreds of times with more species of fish than I can remember. Be thankful for healthy ones. Let your conscience lead you with unhealthy fish.  I have, sometimes, spent loads of money on treatments. Other times… I’ve fed them to large cichlids. In the wild, weak fish are eaten. Period. Giving them life in a peaceful tank is better than they would ever experience in nature.

[Guppysnail]

I’m sorry you are having this issue. I have had this happen with guppies. All are well but one struggles. Unfortunately it’s often genetic or an anomalous birth defect. It’s nothing you did or did not do and nothing you can really fix. As my guppies grew whatever one seemed less energetic or smaller showed defects such as spinal deformity or tumor. 
I always separated those to a tank where they could not breed so if it was genetic it’s could not pass on. I would keep them as happy as possible until I noticed a decline in quality of life. I defined that as struggling to swim or get food or just noticeably unhappy. 
The other side is many breeders or folks that do not have ability to set an extra tank is euthanasia as a kindness knowing that their quality of life is already less and they struggle more to survive. 
Im sorry I don’t have happier news. Perhaps someone with platy breeding experience will have better answers for you. 

[Colu]

Your kH looks low I would try and raise it by adding aragonite or crushed coral as lack of minerals can cause a lot of health problems in livebearers it looks like a growth with  the bulge  on one side the fact the fish hasn't grown much or put on weight  the prognosis isn't good  nothing treatment wise I could recommend I think this might be a case for human euthanasia if you think it's suffering I would use clove oil  sorry I couldn't be more helpful @iwanttostayanonymous 92074