Help! What happened to my plant?

[arctic.violin]

The leaves started turning yellow a few days ago. I made sure not to overwater. I think it may have been that I waited too long before watering again and the soil dried out. The plant is still in its original container which is a white plastic container. Is it sunburn?
Any advice or suggestions will be helpful. I probably did something wrong.

 

[Marck]

If you are certain overwatering and poor drainage can be ruled out, and you suspect the soil has become over-dry. Try soaking the pot in a bucket of water overnight, weigh it down if it floats. It seems quite counter-intuitive, but symptoms of overwatering and underwatering can mimic each other. I doubt it is sunburn as the less exposed leaves are the ones dying first.

 

[arctic.violin]

If you are certain overwatering and poor drainage can be ruled out, and you suspect the soil has become over-dry. Try soaking the pot in a bucket of water overnight, weigh it down if it floats. It seems quite counter-intuitive, but symptoms of overwatering and underwatering can mimic each other. I doubt it is sunburn as the less exposed leaves are the ones dying first.

Alright, I'll do that. Thanks!