Of my 9 plants, the yellow pear appears to be on it's way out:( Haven't been able to get one to live for at least 4 years. I gave one to my neighbor, and hers is doing very well, which really makes me mad!

2 of my Big Boy plants have yellowing leaves near the bottom. Otherwise, the plants look healthy. Should I remove the entire branch where the yellow leaves were growing? Anybody know what might cause this yellowing?

TIA