Sometimes, even if daytime is hot enough, the night time conditions may suddenly turn colder than it likes, with the morning dew, black tip fungus happens. At times hard to control it, it just happens, so it impedes further growth. It only takes a brief exposure for that to occur unfortunately.
Typically if I see that happen, I try to feel the entire stem, if no soggy part, then I just do a bit more watering interval for the time being, till plant recovers. Got to help it feel more warmth/heat all over, and wait patiently once more. It is still summer anyways, so it may still bounce back late in the season though it may be too short to expect blooms since it will be in recovery stage.
