I bought 3 of these guys a few weeks back and 2 of them appear to be a bit on the tubby side, i'ved also noticed that these 2 have the better brighter colouring.
Botias are bred commercially, but it requires special techniques including hormone injections. They do not readily breed in captivity. What they do do is pig out on food to the extent they sometimes look like they're going to explode. A further possibility is that the fat one has been damaged or has some intestinal blockage - is it still feeding?
I also have a Botia striata that looks like it swallowed a double decker bus!!!
I have had it for about a year and at first all went well, but the last 3 - 4 months he/she/it ? just keeps getting fatter and fatter. Appetite is ok, it doesn't pig out more than any of my other loaches, and doesn't look ill or lethargic.
I have absolutely no idea what is wrong. Will try and lend a friends digital camera and take some pics