What are your water stats? How long has your tank been running?
Balas shouldn't be kept in a 10 gallons tank.
3 of them are best kept in a 75 gallons(but this may still not be enough). You are adding too many fish for a 10 gallons tank.
More bala info:
They grow to 30 cm max and as they are quite skittish and tight shoalers, they are best kept at around 6 to increase sense of security. For 6, the minimum tank size required will be 150 gallons, not anything else below.
They are jumpy which requires cover lids on your tank.
I'll be adding that for a 10 gallons tank, only neons and lemons will easily fit but neons are best added once the tank establishes around 4-6 months.
Hooky, it's best to research the fish first before you buy it. If you didn't, it's Impulse Buying which will lead you to troubles due to compatibility, space and other issues.