Q.Can You Tell Me What Could Be Causing This Problem With My Red Star Cordyline Leaves? I Have Tried Pesticides But No Change And N
o sign of pests. Thank you.

Certified GKH Gardening Expert
This does appear to be an infection. Many infections will require consistent fungicide use for several weeks before it will start to resolve itself. Keep in mind that older, infected leaves will never recover. You will know that the fungicide is working when new leaves stay unaffected.
Here are some articles that will help:
https://www.gardeningknowhow.com/houseplants/ti-plant/red-star-dracaena-care.htm
https://www.gardeningknowhow.com/garden-how-to/info/using-fungicides-in-garden.htm