Tricho unwell with yellow, mottled skin

[wachumacallit]

 First time I've seen this plant, at a relatives' house. There are a few there like this, yellowing but with darker mottled patches, all looking a bit stunted. I'd love to know what the problem could be. Too much sun, was my only thought, as it's fully exposed. 

[SayN]

bad soil?

[Strontium Dawg]

It's covered in sooty mildew

[enohpi-zeekim]

It's a common issue with the variety but you can help lmit this by keeping them in a well drained healthy soil.   They need soil with nutrients but it is best to be easy draining.  it can be due to the temperature and humidity as well but they generally like a sunny position obviously don't over water, let the soil dry at least on the top part before watering.   The soil should not become hydrophobic but they should be able to resist drought for short times.  I am not sure I can tell you much more being that it is such a hands on thing for me so without seeing the conditions and soil etc thats about the best I can tell you.  I am not on here often, I last visited 3 or four years ago so all the best.

[enohpi-zeekim]

Sometimes this can be skin damage.  Sun burn after keeping in a dark place too long or being damaged by something brushing against it hard.  Something else to keep in mind.