It isn't easy to see from the pictures for me, but could be oedema, which can be caused by watering too often. Your jade at least is rather drought tolerant and should generally be kept dryer than wetter, especially if kept in a humid (not sure what "tropical" means to you...) environment.

You can google "oedema jade" and find plenty of pictures to compare to your damage.

Sorry, but that 1st plant is NOTa Jade, it's a Portulacaria afra (commonm name Elephant Bush). Pls. do a search for it, I think the watering requirements may be a bit different from that of Jade.

imontestella,

Thank you for pointing that out, I hadn't noticed.

Yes my watering advice was for Jade, and does not apply to Portulacaria Afra. I don't currently have any Portulacaria Afra, so will let others give watering guidance and diagnosis of brown spots.

Daniel

The plants in the second picture look like a Pachyphytum (lower half of pic) and Echeveria (upper half of pic). They really aren't cacti but sometimes people refer to desert plants, generally, as cacti. Also, not sure why but some people seem to avoid saying 'succulent'. I'm guessing your climate is humid so things don't dry out fast. Also, the top dressing of white rocks might keep the soil too moist between waterings.

Thanks a lot guys! I really am struggling on looking for tips to raise succulents in the type of climate we have. I have other baby succulents at home and they seem to be growing well. Maybe its the rocks. I'll move them to something not so enclosing then.