Don't start feeding until the cotyledons start yellowing. It's way more likely that you're overwatering or just came across a genetic problem. She will grow out of it! Watch the watering and pH and she will be good. The cotyledons usually start dying around day 20 or so.
Hey, the yellowing on the bottom shows you she needs a bit of cal/mag nutes. If you don’t want to start any other nutes year, just start with some of that. Happy growing