Tank of DEATH :/

[rreekers]

so i have this 29g tank, it is a live breeder tank. and its sole purpose is to hold fish so they will breed, then i remove female right before they give birth, save the fry and put her back and move the fry to my 20g fry tank. then once the fry are big enough that they become a threat to the newest fry they go into the 29g. Tank is cycled, has been set up for over a year, housed 2 fancy goldfish until 1 month ago, then i put the live breeders in there. the adults were all new, purchased from the LFS on 3/10. all the juv. (3/4"+) were moved from the fry tank. please dont lecture me on the stocking numbers, i do water changes at least every 4 days and have plenty of filtration.
filtration: Aqueon 30 and AC 70
Heater: aqua top 200w i think, i know over kill but lower setting and it maintains constant temperatures
Lighting: stock bulb
Substrate: black blasting sand
decor: some driftwood and a few plants
Temp:77F

Water Parameters as of 10 mins ago
PH 7.7
Nirtites:0
Amm: .25
Nitrates:5

Stock: (as of right now)
Platies: 2M 5F
Dalmatian Molleis: 2F (male died today)
Guppies: {(1.25") 5F} {(3/4") 2} (Dead today- 3 around 1.25", 2 3/4-1")
Nerite snail
gold dust molly juv (3/4") 3 (had 7 about 25 days ago)
Ghost shrimp added 20 (2 days ago) took out 14-16 dead today

so im really confused, why i keep loosing fish, up until today it was about 1 dead fish every other day or so. and it was generally a juv. so i didnt think to much into it. but today i pulled out 2 adults, 3 or 4 juv. and 14-16 dead shrimp

i have the same process with all my tanks and this is the only 1 of my 4 that i have deaths in... i just dont know .. hmm .... there is no physical sign of sickness, plenty of oxygen, they are fed at least everyother day, i always add prime, match water temp by touch, when ever i find a dead fish i do at least a 50% water change, i just dont get it

any ideas?

 

[rreekers]

the tank



average size fish that has been dying




note: I just did a 50% pwc and along with dead fish found that I listed above, I found 3 other dead stuck to the back of prefilter sponge on intakes of filters

 

[Chronos313]

Could be bad stock, could be the ammonia in the tank. Could be bullying. The factors are endless

 

[rreekers]

bad stock explains the ones I bought but not the almost daily deaths of ones that were born in my tanks and survived months with no deaths. Ive never seen any bullying( but I know that doesn't mean its not happening .. at .25 of ammonia I don't think that's it ( just based on previous experience with my fish?