Pale hibiscus flowers - update in OP

I've got an orange hibiscus that I've had for several years. It is in a pot and we put it in a greenhouse every winter. This spring we took it out, trimmed it back, and its flowers this year which or normally orange are now a pale yellow.

We fertilize it every few months, including last month when we put it on the back porch.

Is there some nutrient im missing here or what?

Any help is appreciated.

TIA.

ETA:

The answer

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Hibiscus flower colors, like the colors of most flowers and fruits, are made up of three basic pigment groups: carotenoids and two types of flavanoids - anthocyanins and flavonols.

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Carotenoids ~ The Yellow, Orange, Red Spectrum

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Carotenoids increase production in response to heat and lots of sun. The hotter and sunnier the weather gets, the more carotenoids a plant produces, the brighter the oranges and reds will get. When weather cools off, carotenoid production decreases, and colors become softer oranges and yellows.

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