It looks like you have a great place for them with irrigation and mulch and good soil.They look happy. Hope they don't get so big that it is hard to get them back into a pot of s-h!
BTW, I read somewhere that Euphorbia milii does great in s-h and so I tried one of mine and, you know, they do! The hot summer is hard on Euphorbia milii here, but the one in s-h is not suffering at all and making nice new green leaves now. Usually it just sits in the summer and waits for cooler nights. We have even been running records high lows of 90s at night and still it looks very good!
I have a lot of euphorbia in s/h and they do do great. I could never grow the E. Knuthii before s/h. They would rot on me. I put in in s/h and it has grow happily for years with no problem. The first photo I have a E. decaryi and the francosii. There is a large E. obesa at the end of the rack. The E. knuthii is on the bottom right shelf.