Hi Rachel, it doesn't sound like you're doing anything wrong, or that your sourdough starter is spoiled. It's not unusual for sourdough starters to smell funky early in the process as they gradually weed out unhelpful bacteria, so try not to worry about the aroma at this point. However, it does sound like the early rise you observed might be due to a type of bacteria that gives off carbon dioxide, which, unfortunately, seems to be linked to a delay in the wild yeast kicking in. If your starter stops rising, but is still bubbling, this might be what's going on. While not an insurmountable problem, this lull in rising can go on for several days or even longer.

So, you have a couple of choices here. Since you're still so early in the process you could start over with a starter routine created by microbiologist and sourdough baker, Debra Wink, who discovered that lowering the pH of the starter environment seems to help ward off this type of bacteria, and allows the yeast to kick in more on schedule. Her plan is called the Pineapple Juice Solution. 

You also have the option to continue just as you're doing and trust that the organisms will work things out eventually. Patience almost always pays off when it comes to creating a sourdough starter, so this is also an acceptable route. If you're worried about using up too much flour during the creation process, you could consider reducing your starter, at least until it begins to rise predictably. 

Another possibility is to adapt your current feeding routine to increase the acidity of the starter (as suggested by Debra Wink) in order to pave the way for the yeast to join the party. Here's this plan:

1. Feed once a day.

2. Feed with whole wheat or whole rye flour, if available. 

3. Feed with a ratio of 2 parts starter : 1 part water : 1 part wholegrain flour, by weight. For example, with our smaller starter routine a typical once a day feeding would look like: 30g starter + 15g water + 15g wholegrain flour. 

Once the starter begins to rise predictably (twice) it's important to resume twice a day feedings, which will further promote yeast activity. You may also want to gradually transition to feeding with unbleached all-purpose flour, and increase the water/flour portion to line up closer to the 1:1:1 ratio, by weight we recommend in our sourdough starter recipe. 

It's not unusual to see some delay in rising as the starter adjusts to a new flour or other changes to its routine, but once the starter is rising predictably with the twice a day feedings, and has a pleasant aroma, then you can consider your starter mature and ready for baking bread! 

I know it sounds like a lot, but whatever route you choose is almost certain to work out in the end. Try to be patient, and let us know if you have more questions along the way. 

Barb

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