one other note: i've read in a couple of forums that excessive nitrogen can cause bacterial spot, which perhaps this is. As an aquaponic system, the number one nutrient is nitrate (a form of nitrogen - ammonia in fish waste is converted to nitrite then nitrate by beneficial bacteria). Could this be the issue? I've read that the treatment is often a copper-based solution, but because the system is closed loop, I can't treat with anything that could harm the firsh.

Thank you bboy. I looked up solenostemon and the picture is exactly what I was looking for. Thank you so much for your help and saving me a lot of frustration.

Any general balanced fertilizer would be fine, like an 8-8-8 or 20-20-20 etc. You can cut them back, but if there is still a good bit of undamaged leaves then I would leave them until new stems appear. It is a vigorous species and if taken care of it will sprout new shoots soon. Tim Chapman

It looks like a pest problem to me. I grow hoyas outside , which means that mine are continuously subjected to varying conditions - good and bad. Just keeping up with aphids this time of year is exhausting. I had a good look at my obovata. It shows a couple of leaves with similar pattern. I don't know for absolute certain , but it looks like some type of leaf miner to me. Determining which pest can be difficult, because there are hundreds of flies , beetles and moths which mine leaves at their larval stage. Leaf damage can show patterns that are long and winding, blotches or galls. The 'mines'can be an entryway for fungus or bacteria , eventually causing a leaf to turn yellow and then fall off. A systemic pesticide like Orthene will work, but I wouldn't recommend this in a case like this , because usually with a houseplant, we discover the 'evidence' too late. This part of the life cycle is quick. The larvae have pupated and 'left' !! So the plant gets 'toxified' for no reason. Many nurseries, esp. the Big Box stores are 'trigger happy' and they'll give you plenty of advice on how to solve problems with dozens of products. Remember , they're in the business to send people to the cash register with a smile and an opened wallet ! I am very biased in favour of Denise's ideas. Put the plant outside. Let it get fresh air and all the natural elements,( not fire ! ). I see very little leaf miner damage on anything in my yard, because I strive to create an environment where I rely on natural predators like birds , spiders and parasitic wasps. I would nurture some new cuttings and find a suitable place outside , where the plant can 'enjoy' the summer. Florajilly