Silent killer?

[preyas1207]

Hey guys, theres been some havoc happening in my tank my female guppy first died as she was a bit bloody and had a large white patch on her side then, my two otocinclus died yesterday, my other female guppy had died now today my other female had died the same way my first female died in the afternoon though i looked at one of my feeder guppies (quarantined) and he had the white patch red under his pectoral fins and red near the white spot please help!!!
Who do you think is the killer?I think its the danios especially longfin
Inhabitants
-zebra danios 4 ones a longfin they all nip at each other
-1 male guppy is still alive not a suspect his fins are nipped
-1 apple snail the danios attack him his trapdoor broke off......
-a few ghost shrimp less than 6
-1 male betta he does flare a bit...at him self not really fast and hes pretty shy he has been nipped aswell now he hides quite a bit
-13,12 or 11 guppy fry their in a breeder so not them
i decided to seperate the danio in my turtle tank...... theyre everywhere! they decided to gang up with some rosy red minnows in the tank ones a 2 month veteran

 

[Cynic]

Sounds like a fungal infection which is normally a symptom of insufficient water changes...

 

[preyas1207]

i dont think its a fungal infection i do 30% weekly changes and its not like a patch somewhat swollen it's actually sunken in