I'm a complete layman, but any hints on what might cause this? The app suggests thrips, but I couldn't find any on the plant, nor could I find any of the other suggested symptoms.

Looks similar, but we haven't used any pesticides at all, nor any other chemicals. Just tap water... It's a very sunny place, though, but thought tomatoes could barely get too much!? Could it be "sunburn"?

Michael Have you applied any fertilizer ?

Not even that. Well, fresh soil, mix of some varieties incl special for tomatoes. They likely contained some fertilizer. Nothing beyond that.

Great insight dear Venkat and thanks for the probable assessment ! Let me add a few: Dear Michael, I should request you to ck your growing media or soil or compost if there's excess of moisture or issues like over watering or your pot has a hole though, but may be not functioning as well, as a result root might be in a position to start rotting. Subsequently, the crown area (in between root and stem) start to dry and nutrients uptake slows down when first symptom of leave scorching or blighting may be visible in older leaves, but the younger leaves will show no symptom and look healthy, because younger leaves still get nutrients from upper stem, branches and twigs. Now I should recommend you to repot this plant immediately to a new pot and you have to maintain optimum moisture in growing media. I'm informing you it from my practical experience in pot cultivation. Pls ck in my method how to repot in my next post. Hope that it helps 😊

Hi Michael, Pls ck it in repotting a growing plant. How to plant a sapling. A lot depends on the method of planting. If the saplings purchased from the market are in a polythene bag, then the plant needs to be soaked in bucket water for 2 minutes before planting, so that no roots are injured. The broken brick is to be placed over the tub hole, and to be filled with brick chips 2 inches thick. Then cover with an old cloth. Then place one inch thick sand. Now plant the tree and fill it with soil mixed having nutrients rich manure and compost. Water and air circulation goes accurate due to the sand and brick chips. It provides long-term benefits. 😊😊

Sali thanks. I checked, not sure whether to that was "excessive" moisture, but maybe... I improved the holes/added more in lack of spare ones. Will monitor how it evolves and feed back if that helped saving the plant. Thanks both for your support!

Welcome always Michael 😊