Okay, as advised I repotted my adeniums with a more well draining soil mix. I took the standard cactus mix and doubled the volume with added perlite and coarse sand. How does my new soil mix look? Gritty enough?
When repotting I noticed the original cactus mix was quite soggy with a lot of retained moisture. Thank you
@tarev for pointing it out. I inspected the roots and things looked fine. Caudex feels firm and I didn't see any hints of rot.