Feeding grindal worm only
 

Hi guys, I recently acquired grindal worm and have been cultivating it nicely, I have been feeding them to my betta with lot of spare, the thing is one of my male betta have got lymph behind the gill, though it have gotten better also noticed another one of my male betta have gotten some sort of black dot on the body, I suspect becomong lymph also.

So, basically is grindal worms causing lymph or the food of the grindal which is dog food causing lymph?

Thank you