It could have gotten to dry sitting in the sun a while back and desiccated the leaf tips, but didn't show immediately. You water and treat it well, the past damage then becomes apparent about the same time as new leaves come out ???
In my experience, new leaves are more susceptible to fungal infections than mature ones --> not fungal.
I've had some plants that would do something similar to this when water was left on their leaves (rain or incidental sprinkling by me). Even though immediately spraying with my fav peroxide solution nixed it, there was a clear pattern of browning on low hanging leaf tips. You've got older leaf tips going every which way, so it seems unlikely to be a similar issue --> not fungal.
Root anoxia will clobber all the foliage. Young foliage will be weak and sickly --> not 'over-watering'
Like pyracantha, my coto blows off old leaves until the start of flowering which was 4-6 weeks ago now --> not normal leaf ageing.
So, by my thinking, you let it get too dry a while back. If you do it again, your new leaves will follow the same course. Of course, all it takes is one dry day that you're just a bit late giving it water, so you might relocate it to a bit shadier location or cover the pot with something that will reduce evaporation directly from the substrate to the air. Regardless of what you do, those damaged leaves are permanently damaged. The ageing of new leaves is your 'barometer'.