Why did my bala shark die?

Well my bala was only like 2 inches. He was in a 20 gallon tank for now but i was going to move him along with my other fish to a 60 gallon tank. My fish tank includes: 1 clown loach, 1 pleco, 1 other bala (about 4 inches big) and my other bala that died. The temperature is 78 degrees Fahrenheit. I don't know the ph level or water hardness. I am going to borrow a machine to check them tomorrow. My tank has good filtration and no harmful chemicals due to living in the Country :P If you could give any tips on why he died for now and ill get back with the ph and hardness tomorrow, Thank you. I don't want my other fish dying.