Looks like fongus, or some disease, I use bayer disease control for flowers and plants concentrate used as directed, find it in any store like lowes or home depot

Hi Melody!

I'm not sure what that is but I would just pluck that leaf out and keep an eye on that plant. If possible, place it away from your other plants in case whatever that is is a jumper. If it is something viral, there really is nothing much that can be done.

Personally, I am big on culling distressed seedlings that I can not sort out after months of trying various solutions.

I also bought a cheap plastic hand-held microscope that magnifies to about 60-100x for when I am curious enough to look reeeeaaaaally closely. Often I find crawling things that are easily killed with soap spray. Sometimes I don't find anything and when the issue persists and the seedling continues to deteriorate, I just get rid of it.

Keep us updated!

Pagan

I adopted this poor plant. The woman said it is a desert rose. She had no more info. The leaves turn yellow and drop off. I repotted it 2 months ago. I can't bear to watch it suffer.

Wishepoo, hello there. It certainly does look like you have been gifted an Adenium aka Desert Rose. The first problem I can see is that it is vastly over-potted...unless it has a massive root ball that almost fills that pot? A pot with a diameter equal to the span of the branches would still be generous I think, reason being is the more unused mix you have, the greater the chance of it staying wet, wet mix then equals root rot, something it 'may' have. That said, we can't see how deep the pot is, it could well be shallow, but I don't think it is somehow? Is the mix gritty and fast draining, what did you use in it? Bark, perlite, grit and a small amount of a fast draining compost is recommended. A forum search on here (see towards the bottom off main forum page) for 'Al's gritty mix' will give you a recipe for items you can buy in the US as they have different names to me here in the UK. Water needs to almost run straight out again through the drainage holes...I hope the pot has some? How often is it being watered? Has it been fed?
If it was mine, I would un-pot, check the roots for signs of rot, cut off any dead/dying/brown roots, re-pot in a much smaller pot in a fast draining mix, water thoroughly, once, let it drain and not water again till you think it's dried out completely...then wait a day or so and then water again. Dribs and drabs of water don't work.
Sorry to bombard you with questions, hope I don't come over as being tooooo critical, just trying to help ;) ....also....realise you posted under a 'needing help' thread, but maybe better to start a thread on it's own for a new subject like this, then you will get specific advise pertaining to your own plants probs...again....just trying to be helpful!!
Gill UK

Thank you Pagan. I cut all the problem leaves and I will keep my eyes on it.

Melody

Hey there Greenclaws, I have removed the rotted roots and as many brown mushy root matter as possible. i also sprinkled cinnamon on the newly exposed flesh (another recommendation on Gardenweb). I got the soil supplies you recommended and have repotted it in a smaller pot. I assume it will go through a stage of shock and then rebound (fingers crossed) . I will post another picture in a month or so if it survives. Thank you for your detailed response!