Feingold help please

[JennyC]

Ive had Isa on Feingold for 5 weeks now, she was doing wonderfully. She stopped with her night terrors, her hyperactivity is down and she is just a more agreeable child. However I gave her grapes as her first stage 2 fruit, she went bonkers with hyperactivity so we took her off the grapes and after a few days she is great. But the night before last and last night she started with night terrors again (the first in a month) it was only once each night and thankfully before her dad and I went to sleep but its boggling me why she is starting up with them again. She hasnt had anything new. Any ideas?