Hello moms! My son has had this spot on his diapers for five days now…

Hello moms! My son has had this spot on his diapers for five days now. He's been writing less than usual. We did an ultrasound of the kidneys and sent off a urine analysis. Everything is normal. What could be causing this? I give him vitamin C Cevikap, and we also have a cold, our phlegm hasn't gone away for two weeks. We were diagnosed with obstructive bronchitis, initially we took Zitmack, we do inhalation with Berodual and Pulmicort, drain massage has been done for 8 days but the phlegm is still a lot. Nothing helps. We drink water. There's no coughing or fever, just wheezing, phlegm and shortness of