✦ Starter Troubleshooting ✦
That's not failure. That's the whole cycle, and you looked at the end of it.
A starter rises as fermentation produces gas, peaks when the gluten can't hold any more, and then falls as it runs out of food and the structure gives way. Every healthy starter does this every single time. If she collapsed, she rose first, and that's the part that matters.
What to do. Nothing, except adjust your timing. Note how long she took to peak and use her before that point next time.
If she's collapsing faster than you can catch her, your kitchen is warm. Feed at a bigger ratio to slow her down, or use cooler water.
Worth knowing. A collapsed starter still works, she's just past her strongest. If you want the best rise in your bread, use her while she's domed and still climbing.