I doubt it’s COVID Does it have a fever

doesn't look like something you want to keep...what soil is in the pot? natural garden soil used in pots often has unwanted extras in it that are only revived when they enjoy the TLC that you will be giving your tomatoes but once the tomatoes are over about 10cms tall in warm climates they should really be in ground in full sun...try tipping it out of the pot and cut off about a third of any straggly or broken roots and try planting in the ground with a drenching of seawood and/or carp solution

Or dispose of it and replace with a new one, may have a fungal disease that could infect your garden.

All I can see is an ants nest and algae because you are growing in a clear container. Why are you doing that?

Oh no, sorry to hear about the mystery issue with your tomato plant! It's awesome that you're diving into the world to grow tomatoes, though! The clear container is a unique twist – good thinking!About the ants and algae, that's quite the unexpected company for your tomatoes. I'm no expert, but maybe the community here can lend a green thumb and help you troubleshoot. Have you tried checking if the roots seem healthy? Sometimes that can offer a clue. Happy growing, and hope you get your tomatoes thriving soon!