When the heat turns up, as it probably is now in south Florida/Miami, many potted plants start to suffer. People scratch their heads because the plants have been doing fine up until! The cause is often over-heated roots. The roots of potted plants, especially plants in dark or black pots, are not in the same condition as if planted in the ground. Roots in the ground stay cool. Roots in a pot get heated up - and sometimes cooked. So no matter how much water you provide, they may still be unhappy. We commonly have posts about this time every year regarding potted hibiscus. Hibiscus are a full-sun plant - but not in black pots, LOL.

I don't have any crotons, or experience with them, but this might be the case with your plants (?). As with any potted plant that is suffering, I move them to shade until they recover. I hope yours bounce right back. There are some croton experts here (Fawnridge, we're calling you!) so hopefully they will chime in.
Carol in Jacksonville