Lumps on chromis

[Mrt88]

Hi all.
I have an issue with my chromis in my QT tank.
I have had them in there for a few weeks and I have spotted a white lump underneath a couple of them.
I have had one die about every 3 days and have lost 3 so far. I have managed to get one crappy photo that I have attached.
I have treated daily with Paraguard but no change. Can anyone help ?

Thank you

 

[ndrwater]

Possibly lymphocytes.