As always, answering from a distance is not easy: there is a lack of useful data to get a better idea. In your case it would be important to know how many days you have transplanted. This is quite normal: the seedlings just moved from the seedbed to the garden suffer the transfer: they must root in new soil.
The shock of the transplant
Transplanting in August often adds to the problem of heat, even if in your case at least the seedlings write me that they are in partial shade, so I guess it is less felt. Keep in mind that fennel lives at an optimum temperature of twenty degrees.
I advise you to continue watering daily, taking care to wet only in the evening or very early in the morning. Furthermore, if it is very hot it is advisable to shade the small fennels. If the problem with your fennel plants is simply a post-transplant crisis, they will come back with their heads held high in a few days.
There is also the possibility that there are other problems, for example if you have fertilized too much or with unripe manure, in this case, however, the seedlings should "burn", not simply go limp.
I wish you a good cultivation, I leave you a couple of articles that may perhaps interest you:
- How fennel is grown.
- How seedlings are transplanted.