Bug w lightning

I made a procedure so that whenever my custom mob is hurt, it spawns lightning. There's only 1 lightning block in the procedure yet when I bow my mob it spawns so much lightning my game nearly lags out. To test if it was a self sustaining cycle, I made my mob immune to all 8 things that it can be, including lightning and fire. The same thing still happens, I'm not sure what I'm doing wrong/if this is a glitch.

btw I'm 100% it isn't just a normal amount of lightning, i have a decently bulky computer and have def felt normal minecraft lightning