Poor little guy - he just found out american idiol judges are slated to be the intruders on the next big brother in a segment called Monday night Sumo Sage Wrestling.
plenty of reasons or causes bud, if you cant find one, make one up.
*Im not up with a stocking list, shrimp & nemo? (sounds like a cool dish)
*Anything else effected?
*Nothing you have played with prior to that night, nothing on the hands, no spraying in the house with domestic goods ect ect.
*You didn't have Jaws playing on the TV did you - that will do it every time!
*Flow Input & outputs, heaters ect ect, no chance of environmental impacts?
*intestinal worms...?

yuk!
Look reality is unless you get him/her on the opperating table & examine him/her alot closer its like clutching at straws & taking pot shots or an educated guesses based on info provided.
Last but not least, If he lives in an anem, considering how much & how little we actually know definativly about the relationships, if an anem continues to sting they may very well suffer in the same way we humans do - toxic shock! - Even though more often than not a white streak is visable when they sting the body bad enough in my experiences.