Is the Begonia doctor in?

Is it my imagination, but B.Tiger Kitten isn't looking feisty at all. Just comparing the pictures and the leaves seem to have gotten progressively smaller and smaller. Help...what should I do or not do...?

When it was first brought home.

After 2nd re-potting

After 1st re-potting. On the other hand, the B.Shamus (in front) acquired at about the same time from the same stall at BP is doing wonderful. 

The long and short of it is that the B. Tiger Kitten is no more. After attempting a soil medium change, the entire plant disintegrated. I had to pick out the wilted pieces for the next few days after. Didn't take very long in fact. Not much else I could do. It was such a helpless situation The pot is still there with the contents. Giving it some time to see if a " phoenix rises from the ashes" as the Chinese mythical saying goes.

Begonia close-ups

Turns out I have taken individual shots of my begonia collection. Not all of them but I can add the others later. 

Again names are drawn from Alvin's Journal at greengates.wordpress.com. Thanks Alvin, hope you're still at your begonia craze especially since it's so much easier, with Malaysia being the natural terrain for begonias.

Update (6 Oct): Have added more names and notes as well as absent status of certain ones

B.'Tiger Kitten' - this is no more

B.Black Velvet - this is fast becoming another 'no more'

B. manaus hybrid - looking better. found out it needs terrarium like conditions

B.Rex - this is no more as well.

B. Ice Castle - can tell from this earlier picture that this one is still doing very well. hope it stays that way.

B.masoniana 'Iron Cross' - must be one of the oldest in a collection and in fact pre-dates the craze. Actually it must be the first begonia I purchased. Earlier ones were given to me via leaf cuttings.

B.U400, dubbed a Singapore begonia, started as a leaf from OJ's garden

B.U400 (top); B.Hugh McLauren - this in slow rehabilitation

B.Rex Hybrid - needs repotting

B.Floccifera - can you flower more often?

B.Chloroneura

B.Mazae f. Nigricans - slowly getting there

B.Shamus - so far so good, the best actually. Pl keep it that way.

B. Brevirosa

B. Acetosa - purchased from Tiong Bahru market, with great determination

B. Fireworks - found out that the hybridiser is a certain Mr Kartuz

B. Silver Jewel - a difficult grow

B. Maurice Amey