Shifted result at water temperature calibration

Hi all, I'm doing model calibration process. At this process, I had two strange phenomena. #1. One is that predicted results of water temperature is shifted into right hand side direction comparing to measured water temperature data. The trend is almost identical but predicted results is move to right hand side like parallel translation in mathematics. Do anyone know about this result? #2. The other is that predicted dissolved oxygen fell down zero values unlike measured vales in middle and bottom region. This may be stupid question. Anyway, If there is any idea for this problem, please leave your comment for me. Thanky you for consideration. Have a good day. Yongeun