Yes. They're on a hunger strike. If you put them both in one tank, one of them will be lively and well fed.
Seriously, something is off in the environmental conditions:
. give them greater variation to their diets
. make sure their tails are intact -not split due to bites and not shreddeed
. dechlorinate the water before adding
. make sure you change a portion of their water weekly
. keep the temp consistant and around 78-84 deg F
. keep the tank out of direct sunlight and give them 'reasonbable lighting ' that may correspond to daylight and nightime
See the following link for more details about siamese fighting fish living conditions:
"...primarily carnivorous surface feeders, although some vegetable matter may be eaten. In the wild, they feed on zooplankton including crustaceans and the larvae of mosquitoes and other insects, such as flies, crickets, or grasshoppers. Fish which feed on wide range of foods live longer, have richer colors, and heal fin damage more quickly. Typically, commercial betta pellets are a combination of mashed shrimp meal, wheat flour, fish meal, brine shrimp, bloodworms, and vitamins. These fish will also eat live or frozen bloodworms, mosquito larvae, brine shrimp or daphnia."