Some solutions, specially oganic are good medium to thr growth of microorganisms, like fungs. Try to wash the glasses with hot water before use and after keep the solution if possible, under refrigeration
GO through the LAP single crystal papers ... LAP crystals have the same problem during the growth period and it will be successfully avoided by adding some acids or hydrogen peroxide (which are not react with that solution and its control the formation of fungus)
Especially solutions based on amino acids such as l-arginine, Glycine, L-histidine,l-proline and etc., having this fungal colonies growth in growth vessels. i agree with Thirupugalmani and Silas statement as well as the contaminations in lab should be take care. Precautive measure will taken to avoid fungal contamination of the solution with a help of solutions like H2O2 and ethyl alcohol etc.,