That sounds horrible for you.
My solicitor has said that if I ever get worried about contact I can always go back to her to rethink the contact arrangements, and that it is never set in stone as the children's best interests are always put first.
Hard though it must be though, I think you do need to give it some time for her to get used to things.
However, I would keep a diary of her reactions.
I also think you should tell him, in writing, how she has reacted and ask does he have any thoughts about why she might be feeling like that. Tell him she's obviously found it very difficult and ask how could things be made easier for her next time. Include in the message about sending her favourite toy/ book and about how her bedtime routine is with you so he can keep it familiar for her.
Even if he doesn't respond, at least you are showing your concern and that you are open to discussing things with him in order to help her. If it did go back to court because it doesn't settle down, that would help if you wanted to try to change contact arrangements.
I also have a very difficult ex, who's parenting I don't like. My dd especially was devastated at first about leaving me (she was 5) and would go off in floods of tears. She's recently more relaxed leaving, although can be emotional, stressed and clingy for a while when she returns, especially after a longer stay in the holiday. On the whole I would say things are better (took a few months) but I can empathise with the worry :-(