There have been some very good TW threads. Search - plantar fasciitis
See reply #38 for life style discussion.
I believe that life style issues can be very important. If much of what we do is done with the calves shortened they may become short & tight. Short & tight calves may contribute to problems in the linked muscle-tendon chain
1) Calf muscles
2) Achilles tendon
3) Achilles attachments
4) Plantar Fascia on the bottom of the foot. The most common site of plantar fasciitis is just in front of the heel (see Heelspur link in TW threads above).
Stretching tissue that is still injured(?) is very questionable. Most targeted exercises are intended for conditioning to reduce injury risk and not for physical therapy. That issue belongs with a Dr and physical therapist.
Be aware that there are two calf muscles, the Gastrocnemius and the Soleus. Separate
stretches are required for each calf muscle. Search TW threads for Soleus stretch, etc.