My hibiscus leaves are getting yellow. My mums are yucky-looking. I planted these in pots with last year's soil. Kalanchoe blooms are triggered by short days and long nights. Yours may come around before long.
Crotons are tropicals that are sensitive to cold.
Yours may be reacting to the cool, damp weather we've had. It's a good idea to gradually move your plant indoors for the winter. But we are supposed to get near the freezing mark soon, so be prepared to move yours indoors at any moment. Fertilize with a balanced formula, keep it in bright light and keep the soil moist but not soggy. Hibiscus leaves yellow with age and drop, making way for others to grow.