Hello and hope you are doing well.
It could be Charcot-Leyden crystals, which are minute colorless crystals that occur in the sputum following an asthmatic attack and that are thought to be formed by the disintegration of eosinophils. It could also be due to fungal infections like aspergillosis. Only an evaluation can help diagnose the cause.
Hope this helped and do keep us posted.
I am not really sure to be honest I'd have it looked at