I've successfully rooted 6 dipladenias 4 month ago, they are in pots since 3 month. All went well so far, but now it seems they have some illness or pests. (All the six, although in different progress)
I am an absolute beginner, so I just hopelessly see their day by day worsening condition, and I am a bit worried my original two older ones may also get infected.
Could anyone identify what the problem(s) is/are, and most importantly what to do to cure? Is it virus, or pests? (I do not see bugs neither on the back side on the leaf, and when I try to touch or get something with my nails, nothing detected (but again this is the beginner speaking)
Detailed plant and environment info:
Location is Budapest, Hungary, it's autumn first month September now, temperature is approx 25 C / 77F, now, the pots are in very well lit outdoor place. It seemed to me that dipladenia (both the older 2 and also the 6 rooted very flexible for water supply, never dropped a leave since spring, they got relatively less water.
I prefer use only absolutely harmless chemicals and methods, as I have no appropriate protective gear.