Leaves on 2 different houseplants are turning yellow and splotchy.

Both plants, a Dracena and a Money Tree, have been thriving in my rather extensive plant collection for over 4 years. They’ve more than doubled their sizes in that time.

A few days ago, I noticed that leaves on the Dracena were becoming yellow and with many even lighter splotches. Then yesterday, a friend who was visiting noticed that the MoneyTree leaves had started looking yellow and splotchy. She touched those leaves and said they felt a bit sticky.

What could be going on here, and how should this be treated? (I have one photo but don’t know how to add it!)

I’m now worried that this condition, whatever it is, could spread to other much more extensive and difficult to replace plants in my collection. Help!!!