orange streak

Hi, I'm a newbie to bread baking and have learned a lot from the accumulated information on this site. Hoping someone more knowledgeable or experienced can advise me on this.

About 1 1/2 months ago, I created a starter using whole wheat flour and pineapple juice that I eventually converted to a white flour starter. I usually keep about 60g of starter, retaining 10g and feeding it with 20g water / 30g bread flour about once or twice a week. When not feeding, I keep it in the fridge. I've made a few experimental loaves which have turned out ok (at least by my novice standards).