I have a Sun Coleus that purchased from Home Depot two years ago. This plant is very delicate, and has very
|Sun Coleus is unique in that it does need a lot of strong direct sun to stay healthy. In too little sun, it will grow leggy and weak. To rejuvenate it, you could try cutting it back quite hard and repotting it. Use a good quality container mix formulated for container plants. As it regrows, you may need to pinch back the tips from time to time to help it stay dense and bushy.
Philodendrons as a rule need moderate light -- bright but indirect is great. Direct sun can sunburn it. Yellowing can be due to excess direct sun, lack of nutrients, or possibly a pest problem such as spider mites. Check the plant for signs of insects such as fine webbing on the undersides of the leaves. These can be treated with commercially formulated insecticidal soap per the label directions.
When a plant has been in the same container for a long time, repotting into fresh soil or replacing a bit of the soil in the container can sometimes be helpful. Also be sure you are watering correctly, as yellowing can also be caused by over or underwatering. Allow the soil to dry somewhat between thorough waterings. Use your finger to dig into the soil and see if you need to water. Empty the drainage saucer under the plant after you water so it is not sitting in water.
Both of these plants can be fertilized regularly with a general purpose water soluble fertilizer such as 10-10-10 plus micronutrients. Read and follow the label directions for how much to use. Use the lower rate for maintenance and the stronger rate in the summer months when it is growing faster. (If your potting mix included a slow release fertilizer, then you would not need to fertilize for the first few months -- check the label on the potting mix.)
I hope this helps you trouble shoot.