I wish I knew! They came from the nursery unlabeled earlier this year.

Maybe you're more familiar with these? I know it's one of the following:

Valencia Orange - Citrus sinensis

Lemon Tree - Eureka "Four seasons"

Key Lime tree (Citrus × aurantiifolia)

Meyer Lemon tree (Citrus meyeri)

Honey Tangerine tree (Citrus reticulata 'Murcott')

It's probably Key Lime then.

thanks!!

I agree, I'd look at the soil mix first. I have also grown things in solo cups, and they are not my first choice for citrus. If you use them, be sure to add lots of extra drain holes.

I think you should probably wait until that turns fully black/brown, but generally, 'dieback' should be cut off. Clean your clippers with alcohol before and after.

Pests could also be a cause, and spider mites are particularly hard to see. Especially if you had them in a grow tent, there might be reduced air movement, which helps the mites thrive. So, add misting and air movement.

As far as identification goes, all of my lemons and limes smell like either lemon or lime fruity pebbles. If you tear a leaf or segment where the leaf ripped off, then smell it, you’ll at least be able to tell if it’s a lemon or a lime.