it sounds like your puffer is really stressed out. how big is your tank with the puffer?
if he stays at the bottom he might get the spots from scraping his belly on gravel, rocks or other ornaments.
could your figure 8 puffer be beating him up?
i know once the gs puffer reaches maturity you should put it in his own tank.
you could try out some stress reliever, but try and do more resarch first. i hope it works out, good luck!
