Thank you Lauren for your question to "Ask Extension".  When I try to magnify your picture it becomes a little out of focus.  But I believe that they are the eggs of a spider mite (Tetranychus spp.) and not a fungus.  To help reduce future infestations keep the soil moist and the humidity high as spider mites like dry conditions.  The life cycle of a spider mite can be as short as 8 days with a temperature of 80º and up to 20 days in cold conditions.  I could not find any controlled scientific studies on the particular product that you used but insecticidal soaps are among the recommendations for control.  I have provided you with additional information from the Pacific Northwest Insect Management Handbook for controlling spider mites.
    Management-chemical control: HOME USE

• azadirachtin (neem oil)-Some formulations are OMRI-listed for organic use.
• horticultural oil-Some formulations are OMRI-listed for organic use.
• insecticidal soap-Apply control measures when mites first appear, and repeat application as necessary. Good coverage, especially on undersides of leaves, is essential. Some formulations are OMRI-listed for organic use.
• plant essential oils (clove, garlic, rosemary etc.)-Some formulations are OMRI-listed for organic use.
• ALWAYS read and follow the instructions printed on the pesticide label

     I hope that you find this information useful and as always Happy Gardening.