Sommai Tan, your plants are beautiful! Thanks for taking the time to post. Yes, I am familiar with Marie Tran's portfolio, too. Here's a treat for anyone who has never seen her plants: [Crown of thorns collection[(https://www.houzz.com/discussions/crown-of-thorns-collection-dsvw-vd~1791211) [Crown of Thorns in full bloom[(https://www.houzz.com/discussions/crown-of-thorns-in-full-bloom-dsvw-vd~1825405) Carol in Jacksonville

I hope I read this correctly and understand your question. Your plant IS blooming. Here's the flower - The flower is by your thumb in the second picture. My plant has red flowers so maybe it will stand out a little better for you. Sometimes I only get 1 or 2 flowers on the inflorescence, other times I get multiple blossoms. I rarely fertilize these. They grow in the ground at most homes here. You potting mix looks good and it sounds like you are doing fine in getting the plants plenty of sunshine. My plants are outdoors all year round, but I do find times when the leaves fall off like trees in the fall. I'm not sure why, but figured it is the difference in seasons - dry or wet, mostly. If you haven't already done so, look for little aphids or mealie bugs on the back of the plant and between the leaves. I see a couple of deformed looking leaves, but that may not mean anything. Always best to take a close look. Hopefully someone else will have ideas for you! It looks pretty good to me. (maybe mine looks really bad! LOL)

Here's how mine looks. It has some partial shade, as it is planted near a wall, as you can see. Mine is planted in sandy soil and never gets fertilized, that I know of. Photo is from January 8 of this year. Our annual rainfall is 113 mm | 4.4 inch, but it does get occasional water from an irrigation system. Our climate is also quite hot in the summer and mild in the winter. I think you should put your plant outside during the summer. The fresh air might do it some good. Also, good drainage is a must. I recommend repotting it at least every two years as well, and check the roots, if you want to grow it indoors. The roots need to spread out if you want it to be bushier. I personally do not have experience growing this in pots, but I do have it in my front yard in Los Angeles, in addition to my patio area in Cathedral City.

IMO I would leave them be. I see why you would want to prune, but they are pretty the way they are🙂. The two tallest ones are getting new growth at their bases. So they’re on their way to looking lush. There’s not a lot of room for error with each COT and it would be a bummer if something were to happen. Plus it would be a long time before the pruned plants looked full. They will look like a thorny stump for yrs😉. How are the roots, do they fill the pots? Maybe it’s time for a bigger pot. Not a huge pot of course.