Nitrite and Nitrate spike

[Duds]

Hi as some of you know i have a problem with bristle worms so last night i tried to put a yogurt carton with shrimp in it to get them in there when i got up and looked at the fish tank the bicolor blenny was dead and the spotted mandrin was dead i check the amonia nothing then nitrite it was about medium and nitrate about medium also what should i do to get nitrie and nitrates out?
HELP!!!!
Quick
Duds

 

[this is me]

Water change. 50%
and another 25% a cuouple day later.