leaf curl and yellowing of leaves on Hibiscus plant in-ground

Question

The small plant is named Fijian Hibiscus rosa syneresis.
The others, unfortunately, I don’t know the full names of.
All three plants are in a frost free & sunny position {New Zealand }

Cheers.

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Answer 1

They are very heavy feeders, and will require quite a bit of fertilizer. These articles will help you to feed and care for Hibiscus: https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/hibiscus-fertilizing.htm

https://www.gardeningknowhow.com/ornamental/flowers/hibiscus/how-to-care-for-hibiscus-plants.htm