They were all sowed on the 20th of august, the variegated ones can not make it as they do not have chlorophyll. In terms of size, it may depends on the species and media also, I ever sowed a white color adeniums, after 1 year they only grown to 6 or 7 cm only. That was a wrong species and wrong media. If you use coco peat, just make sure to soak and wash the tannins for at least 2 days.
The media that I used for this, just a mix of husk charcoal, fine lava rock, fine pumice, some cocopeat, and maybe some sand ( not remember), then when they grow about 3 to 4 cm, I added 1 layer of soil again to support the stem to make sure that they can stand, I used a lighter media, husk charcoal, perlite and cocopeat.
For the plastic cover, originally both have the cover, I just gradually adding more holes and finally will open the plastic, maybe tomorrow or the day after I will get rid of the plastic, I didn't open the plastic because last weekend this one is still smaller then their neighbor.
Another note: compare to yours, my adenium seedlings are less exposed to sunlight than yours, this is another reason also that they grow taller, looking for sunlight, those that have access to sunlight will not grow as tall, but they are stronger.
