Hi ... snow white waste = intestine bacteria = bloat.
pale = stressed or sick
thin = not eating (obviously!!!) = stressed or sick

BLOAT
Usually caused by stress or inappropriate diet ... especially for troupheus. In this case, I suspect that it is from stress. The white waste is full of the bacteria, and will soon infect all other fishes, that I suspect, are somewhat stressed as well. Very soon, all your fishes will strart to die. Go to your nearest fish shop and get some medication to treat intestinal bacteria.

When you put in medication, you must remove all sponge filters. Otherwise, the medicine will kill all the beneficial bacteria on your filter.

STRESS
There are many things that will cause stress ... the way you release the fish ... terratorial fighting amoung fishes ... lack of hiding places ... but MOST LIKELY, it is poor water condition. Regardless of your water condition, if you suspect that your fishes are behaving "funny", do a 50% water change every day for 3 days. This will quickly help you refresh your water without over stressing your fishes. Also, add in some plants, be it real or fake, floating or rooted ... just make sure they have somewhere to hide.

PRODUCTS USED
"dechorinator, stress-coat and Cycle brand bacteria" ... I don't really use any of these items. There are many misconceptions in fish keeping:

1. Don't change more than 50% of water. Only under emergency, change up to a maximum of 75% of water. Most people change 100% of water, but this REALLY stress the fish ... imagine the stress if you are in KL, and suddenly, you are thrown to North Pole!!! BIG & SUDDEN change cause much stress!!!

2. Don't wash your filter with tap water. Good bacteria helps clean your water. It takes about 1 month to for the bacteria to establish. Chlorine kills the bacteria, so your filter will have to start the process from scratch again!! Instead, use your tank water to wash your filters!!

3. Leave your tap water in a pail for 2 days. Not only will the chlorine eveporate naturally, your water will also become less stressful for your fish.

4. Your bio load (waste) must balance your filter capacity. Yes, white flakes = bio load > filter capacity. However, as your filter takes about 1 month to fully mature, you must also increase your fish slowly. It is recommended to add 1 fish per week ... something that I never do also !!

Sooo, I think this happened:

1. your bio load > filter capacity,
2. so you upgraded your filter to undergravel filter
3. during the upgrade, one of your fish becomes over stressed and gets sick
4. the white waste full of bacteria is released, and this infected less stressed fishes.
5. Other fishes gets sick, and the cycle continues!!

Hope this helps!!!