There are a few things to look for when determining if your betas are sick. First, check for any abnormal behavior. If they are acting lethargic or not eating, this could be a sign of illness. Next, inspect their fins and tail. If they are frayed or have white spots, this is another indication that something may be wrong. Finally, take a look at their gills. If they are red or inflamed, it is likely that your fish are sick and in need of treatment.