Lievito madre stopped growing on day 5

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Hi, 

My livieto madre was growing great the first four days, doubling every 6-8 hours. On day 5 I left it overnight on the counter and it hasn’t grown overnight. I cut it and saw some bubbles so there’s been some activity but not much. I still fed it in the morning and put it in a warm environment but I have barely seen any growth so far. How can I fix this?