guppy

[flyhockey1037]

i have a smallish guppy, a young one. its laying on the gravel at the bottom and not moving. it is still alive because every once in a while hell swim around a bit. it looks like his head area is getting dark, almost black. im assuming this is not good since he is normally orange.
nitrates - 0ppm
ammonia - 0ppm
ph - 7.6
water changes about every 2 1/2 weeks
no medications
in with 1 pwdr blue gourami, 1 marblehead angel, 1 guppy, 3 neon tetras, 1 balloon molly, 1 hifin black skirt tetra, and 1 red wag platy, 1 otocinclus, lots of snails, o yea 1 emerald green cory.
20 gallon tank.
i added two angels and the gourami a few days ago. one of the angels croaked already. the petco angels really suck. they all die on me. i dont have problems with other fish though.

is there something special to keeping angels? gouramies give me problems too
my main concern is the guppy though? what to do

 

[Jesse]

Maybe due to stress or being bullied around? Maybe just not a healthy fish. I believe guppies are very prone to not being healthy. Might wanna ask a moderator directly, since no one has replied.