They can be tricky. They want water while in flower but once done flowering they like to dry out and go dormant. If you water while dormant you'll definitely shorten their life. They are also very susceptible to ink spot so it is generally recommended not to overhead water. Each fan only blooms once and it's recommended that the fans be cut back as far as possible after blooming is done without damaging the new fans. They want excellent drainage. Then there is the problem that they don't like excessive phosphorus and so many residential garden soils are overloaded with phosphorus from decades of ill conceived fertilization with 'balanced' 20-20-20 fertilizers.

Looks like an old one to me. New stalks tend to be greenish, then develop some reddish fuzz at the ends as they mature, like the current one with the flowers. Old ones loose their color and gradually become more dry and brittle.

I realize this may be too late... but yellow leaves usually mean plants are TOO wet and that you have root rot. Maybe let it dry out a bit more between waterings... also, if you’re fertlizing it, stop. That could also be causing this.

Yes, you should. I don't know about kangaroo paws (aren't they a CA native?) but I'm quite familiar with cutting into / planting in the delightful and rock-ridden SouCal clay pan. I'd contact a local garden club through their website to see if they have tips (normally I'd suggest you join a C&S club or at least attend a meeting, but they're not happening now). Short answer - no sand. NONE, as it's not useful in this situation. The best would be small gravel/decomposed granite and pumice, along with some sieved top soil to use as soil amendments - what you want is some of that clay in the mix, but mostly the other things, particularly the DG and/or pumice. Amend the yard as you need to - the planting locations need it, not necessarily all of it. Oh, and get a digging bar if you're going to do a lot of this. It's invaluable in punching planting places into the ground. I think your chalk plants are Senecios.