Interpretation and how did we do next?

A 27weeks gestation male premie was admitted in NICU 6 days ago, his birthweight was 990g and apgar score at birth were 4 and 7 at 1 and 5 min, severe RDS was onset after 1 hour of his life and the endotracheal intubation was performed followed by the PS administration, he was put on HFOV , a GI tube was inserted and the enteral feeding was started with EBM at the second day of his life, well tolerated. This morning I rounded the ward and found he developed mild RDS manifested by intercostal retractions and the O2 saturation was suboptimal, around 87~91%, so I had to increased MAP from 9cmH2O to 11cmH2O, then his saturation got better and intercostal retractions improved, by auscultation, there are lots of rales in his bilateral lung fields and the sounds of aeration were not equal, the sound of his right side was much weaker than the left, the CXR was attached here, how to interpret it and what shall I do next?