Q.dieffenbachia
My plant is a beautiful gold speckled dark green, but the new leaves unfurling are pale yellow. It started this a week after I had it, daughter purchased it for Mother’s day this year. The garden we bought it from said they had never seen this before and were no help. I am hoping you can shed some light on the problem. The one I discarded had been with me for six years, so you can understand my curiosity. Thank you, Fort lauderdale.
Your plant sounds like it needs more water.
A Dieffenbachia is a tropical plant and needs to have it's soil consistently moist.
Here is a link that will refresh you on the care requirements.
https://www.gardeningknowhow.com/houseplants/dumb-cane/growing-dumbcane-dieffenbachia.htm