Ammonia Spike?

[mark7616]

I just looked into my community tank and noticed that my ram had gone black so is not in a good way so i checked my water and noticed my ammonia was at .50 i have no idea why my nitrite is 0 nitrate is 5 i have not added anything to this tank for well over a month infact i lost 3 mollies and a goby when i was away for a week i did normal water change on sunday havent added any new media to filter so do not know for the life of me where this ammonia spike has come from any ideas?

 

[jarmado]

are all fishes accounted for?
maybe the spike came form another dead fish that you haven't found yet.