Hi, I am a sourdough newbie. I got a small bag of 15-year old starter from a bakery about a month ago and have baked with it for 6 or 7 times since. Still experimenting different ways to keep & feed it, so sometimes I would divide the starter into different jars and feed them differently. So far the starter seems to be working okay. It'd peak at 4 hours if I feed it at 1 : 0.5 : 0.5 or at 9 hours at 1:1:1 or 12 hours at 1: 2.5 : 2.5.
This morning I divided the starter into 3 different jars, all fed at 1:2.5:2.5 (with organic white and filtered water) before being left on the usual worktop (about 24-25C or 75-77F). I was hoping to place them in different corners at my flat later to check for the optimal temperature. I expected the starter in all 3 jars would look pretty much the same, as that's usually what happened before. But I got a bit of problem today. After 10 hours, the starters look very differently. The jars/starters are of different sizes, but all have same hydration %.
(1) 84g in this bottle (14g starter + 35g each of flour & water). Alive but not as active as before. It smells a bit tangier than usual. But the problem is, I am not sure if my "usual" is the right one. Maybe it's normal or even better to smell tangier?
(2) 60g (10g starter + 25g each of flour & water) - Smell yeasty and slightly floury. Not too tangy. This is usually what I regard as "almost ready to use" for baking, not sure if it's true though?
(3) 120g (20g starter, 50g each of flour and water). It smells funny. Slightly tangy but got a strange smell as well. Weirdly it got a plastic-y smell.
I am very confused. I think maybe the last jar has been contaminated as I just washed it with some detergent before drying up and putting in starter. But I am also curious about the following:
(1) what possibly made the first two jars behave differently? Was it just a random outcome or there's some other reasons?
(2) I usually regard the stage as in the second jar starter "almost ready to use". This is how my starter looks at peak. It will get more bubbly in the next two hours but the level will be falling as well. I did read a lot of old posts here in TFL for guidance but still got confused. Some claim the starter should be best used when at peak, while others said it's best used when its most bubbly.
(3) I am not sure about how a healthy starter should smell. Some people said it depends. Different strings of yeasts may smell differently. I remember when I first got this starter from a bakery, it didn't smell sour nor tangy at all. But it's also possible that it had just been refreshed by the bakery so my first impression wasn't its usual state.
(4) One last question about feeding. I have been feeding with the same brand of organic white for the last 4 weeks. But I think I've read from somewhere before that feeding with different types of flour (or at least different brands) would do it good. The starter would have the opportunity to cultivate different populations of wild yeasts and it would benefit the strength and flavour in long term. Unfortunately I couldn't find any relevant articles online to discuss this further.
Sorry for the long post and my poor English. Thanks for reading. Any advice or sharing would be appreciated.