Short answer: No. Mushrooms should not be eaten during Paryushan.

Reason (simple and traditional):

• Mushrooms are fungi that grow in damp/decaying places and carry countless tiny life‑forms.
• They cannot be cleaned thoroughly, so their use risks more himsā (violence).
• During Paryushan, both Śvetāmbara and Digambara Jains follow stricter ahimsā and avoid such items, along with roots, fermented foods, honey, etc.

This is the common maryādā in both traditions. If your local guru or saṅgh has any additional rules, follow those first.

More details:

• Why Jains avoid mushrooms
• Paryushan food rules (items to avoid)