Hi Eoin, the only thing I can think of is to let it feel the outdoors all day/all night long. It has to feel the temperature variance too. But protect from rain, if it has no new leaves yet. Good to know caudex is staying firm. 20C is not bad, that is our Spring time temps here, and it is just a bit of a wait, then once those new leaves show, then you can step up watering.
The heat mat helps for sure, but it really likes much more heat and has to start acclimating more outdoors.
I am not good at seed level. Find the Adeniums Chat thread in the Adenium forum, the other growers who have done seed growing are there. They can help you more about it.
