Hi Mia, when you tripled the amount of starter this likely caused the dough to ferment faster, so sticking to the same timeline (especially the long overnight rise) may have resulted in over-fermented dough that was more likely to be gummy in texture. This is because as the dough ferments and becomes more acidic the structure starts to break down. Whole wheat flour also ferments faster than white flour, so increasing the amount of whole wheat flour would also shorten the overall timeline. It's especially tricky to manage an overnight rise during the summer with an increased amount of starter and more whole grain flour because the warmer temperatures also make fermentation happen faster. 

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