I'll link you to an Overview of Good Growing Practices, which will help you avoid all of the most common pitfalls nearly every grower encounters on their journey to the mountain top. This will allow you to draw comparisons to what practices you have in place, and likely reveal a number of factors you haven't considered or aren't aware of. Ideally, the overview will lead to questions and you can start putting together the puzzle pieces. Trial and error is a painfully slow and ineffective way to learn, primarily because it takes a fair amount of knowledge to connect cause and effect when there is an issue. Learn all you can from a reliable source, then use time spent in practical applications to verify what you already know. I guarantee, if you take that approach, you'll leave the trial and error crowd standing in your slipstream.

About putting the puzzle together ...... When putting a jigsaw puzzle together, most people strive to finish the border first. If we compare the puzzle assembly to growing things, the framework of the puzzle is like the basic knowledge required to grow well. Once you have the basic knowledge assembled, filling in the rest picture becomes much easier.

Al

Zoe, I can't help you with the jigsaw puzzles, but the plant in the last two shots are a variety of Spider plant (the genus is visible in the picture, Chorophytum). I don't grow this species, and don't know if it suckers as vigorously and continuously as the more common species. As you said, you also have Aloe vera (now known also as, Aloe barbadensis). These things grow like weeds for me. I don't know what it is, but my friends seem to manage to KILL them all the time. Guessing overwatering from too much love and attention. It is one of my favorite succulent houseplants. I prefer growing them in clay pots for faster drying, and also like a very loose soil, so added coarse sand and perlite. I rarely if ever feed mine. Let dry between waterings. I think I water mine here at 41 N about every two-three weeks mid Winter and with a LOT of sun actually, even in mid Winter. UK, southern exposure is fine, but further south, they actually can burn in too intense, direct sun, coloration is better in filtered sun, in intense sun, leaves will turn more pale or even develop some reddish tones but I find the deep green more pleasing. These color changes are temporary..., depending on sun exposure. They sucker like crazy, so you can spend the rest of your life propagating them for friends. I am not familiar with the other succulent you posted.