Continued Fussiness & Grunting. Advise.

My 4 month old baby girl has been continuously grunting and fussy since last night. She is otherwise a healthy baby. This is the first time she has been like this. She had only slept for 7 hours since 1am. Her feeding is also fussy. Apart from that she has been shaking her head vigorously from side to side in her sleep and also while feeding. Sometimes she's smiling when doing that otherwise grunting. All these sudden changes are really concerning me. I have noticed her making a whistling kind of noise when she takes deep breath and coughs a couple of times a day. I use nasal drops to clear her breathing issue. As we reside in Gurgaon, the weather and the pollution levels have been bad. We use a air purifier and a humidifier. The room temperature is set to 23c. Why is the baby getting fussy all of a sudden. Please advise.