Ariel,
That is definitely Spider mite damage to the leaves. Nothing you have done wrong. Treat it now and then again in 5-7 days. I have been using Brian's mix which is
1Litre of water
1Tbsp liquid dish soap
1Tbsp olive oil
mix this in a spray bottle and shake vigorously while using to keep all dispersed in water.
Do this in the evening (No sun on it while it is on) and spray off with plain water in the morning or even a few hours later. Spray top and undersides of leaves and even the caudex. They are hard to see and the spray is a contact solution.

Some use just water and dish soap, but I like Brian's because the oil will smother the mites and they cannot get it off. Works well with aphids also.
Rick

Thanks. This is bad. I'm going to have to treat everything outside, because all of the plants are pretty close to one another (I moved this for the pictures). Are there any plants I should be particularly careful about spraying?

Again, thank you!

Ariel,
I have used other store bought products, such as Safer's
End-All, Insecticidal soap and Brian's mix with no ill effects on my adeniums, hibiscus's.
Big thing is to not use in sun and I like to wash off. If it does not kill the insect after a few hours it is not going to.
The product has to get on the insects to work, so rinsing is a good thing.
What I have started to do and it seems to help deter them. Is give my adeniums and Hibiscus a mist of plain water from the hose in the morning of a nice day, just on the leaves and so not to drench them.
The mites and aphids do not like a moist environment.
Not to say I will not have issues at some point.
More frustrating than anything.
Rick

I'm going to give it a shot. Thanks!