Sometimes I do things that seem to make sense, but are actually bad for a plant, like tomatoes in large black plastic containers up against a nice sun reflected block wall. I've made all kinds of mistakes that now I feel I have to ask before I make another, so please forgive me.

I have a couple of yellow Tropical Hibiscus, not hardy, that are doing okay. As long as I snip off the old flowers I get new ones about every two days, but one looks a bit scrawny as far as leaves, plenty of branches, just low on leaves. I've used Foliage Pro to no avail. What else could I try?

I'm also about to plant another, this time red and want it to do as good as my other yellow. First off the soil here is basically sandy garbage in my book. It always has to be amended to make anything grow and then it's still always a fight to keep it growing. The spot I've chosen for this hibiscus is next to a wall that gets sun just after mid-day. I thought if this fills out it would help cover the wall as well as add color at this bland part of my back yard. I've had the plant, still in it's black pot, in the spot for about a month and it seems to like it there as it's stayed dark green with nice big red flowers on it. When transferred to the ground should I expect the same? Mid-Summer SoCal heat? How should I amend the soil, if you can call it that, for best success? Any other advice?

Rather than list everything that I own as far as food, fertilizers, etc., I've included an image of my supplies list that I keep on hand.

Lastly, I have a product called Ultrasol k Plus, it's NPK is 13.7 - 0- 46.3. Since Hibiscus have such a great need for potassium, would this be okay to use?

Thanks for any help