Homebrewing - Beer, Mead, Wine, Cider

I've been brewing lemonade with a ginger bug and water kefir for quite a while. But whenever I try to incorporate lemon peel it seems to completely halt fermentation. I have tried normal and organic lemons without success. Currently I have a small batch of kefir with lemon juice going. Half of the batch is with lemon peel and that half shows no sign of fermentation after 30 hours (I have already bottled the other half because it was ready). Did any of you have similar experiences? I would really like to include peel for the taste 🙃

EDIT: Thanks for the many inputs! Summarizing the responses it seems like lemon peel doesn't inherently stop fermentation and the cause is more likely to be whatever pesticide the lemons were treated with. So I got myself a very expensive (supposedly) untreated lemon which I will use in my next brew (after washing it thoroughly) and continue from there.