Hi and welcome to the forum
How long has the tank been set up for?
Have you tested the water for ammonia, nitrite, nitrate & pH?
if yes, what are the results in numbers?
How often do you do water changes and how much water do you change?
Do you gravel clean the substrate when you do the water change?
Do you dechlorinate the water before adding it to the tank?
How long have you had the sick fish for?
How long has the fish had the red lumps?
What other fish are in the tank?
Have you added any new fish in the last couple of weeks?
Post a picture please?