Thanks for the quick responses! :) I haven't been able to spot any critters on the leaves(? fronds? branches? not so sure about terminology here!) so far. The cactus pictured is an Epiphyllum - I just did some research and identified it. Whatever is going on with it is also affecting my Euphorbia milii - there are little brown spots and holes appearing on some of the lower leaves. I water them sparingly with room temperature water and allow it to run through. They're located close to a window in my kitchen... I don't think it's too drafty there but I could be wrong. There are more pics of the problem in the link. Thank you for responding!

First, you need to know that this plant (and all other Euphorbias) has a very toxic sap that is a powerful skin and eye irritant. If it gets in your eye (e.g. brushing face with back of hand), it can cause temporary blindness. Be careful never to get sap in your eyes, or leave it on your skin. E. tirucalli has a particularly bad reputation for toxic sap, so be careful! Cut at branch nodes. Staunch the flow of sap with lukewarm water. Repot into an 8-inch container using Cactus and Succulent soil (or regular potting soil) mixed 1:1 with perlite, gravel, or pumice. The idea is to make a free-draining mix low in organics, but with more than 50% inorganic particles in the 1/8 to 3/8-inch range. This plant wants as much sun as you can give it. Growth will be much slower indoors. Allow the pot to completely dry before watering. Fertilize 3-4 times a year with any balanced fertilizer at 1/4 the normal strength. Happy growing!

I don't grow this plant, so I can't offer you any specific advice. I am sure you will be asked what type of soil is in the pot. Many problems start there, as most succulents prefer a gritty, fast draining growing medium. The name of this plant is Euphorbia tirucalli. I hope your research told you that this type plant has toxic latex sap. It can cause dermatitis by contact with the sap. Some people are more allergic than others. If it gets in the eye, it causes excruciating pain usually needing medical attention. So now that I've scared you, just be careful in any pruning. Wash your hands and implements well and don't touch your face when trimming or repotting. Spraying any cuts with warm water will stop the flow of latex. Just a little knowledge beforehand to avoid problems! Good luck with your plant!

My rubber tree tineke that I ordered online looked fine the day it arrived and I immediately transplanted it to a new pot with drain holes. I did not watered as I want the plant to settle first on its new environment.A day after, I watered it thoroughly and misted the leaves. Then I saw a small brown spot near the leaf tip. As the days went by, the browning spread further and when I checked on the leaf underside, there are some grayish things underneath. They are circular and seem to be wet and oozing out from the leaf.I've attached a photo of the leaf in the comments below.Can you tell me what are those thingsunderneath the leaf? Is it some sort of fungi or bacteria that I should be worried about?Please give me advice on how to deal with it as I really want to grow the plant.