Answer: Purple winter creeper is generally pest free but if the foliage is changing color and spots are appearing, it may have developed a fungal disease. I would prune out the affected plant parts and then feed with a balanced fertilizer to both encourage new growth and to help green up the yellowing leaves. (a liquid 20-20-20 will feed both the leaves and the roots so you'll see a difference sooner than if you used a granular fertilizer). Pruning out the spotted leaves will not only remove the disease pathogen but will also open your Euonymus up to better air circulation. To help avoid fungal diseases in the future, try to keep water off the foliage.
Best wishes with your landscape.
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