Hi Alli,
Renewing the soil is nothing more than repotting with fresh new soil. Plants kept in containers use up the available nutrients in the soil and the soil itself tends to break down. Using new amended soil or adding compost to your existing soil when you repot, gives the plant the nutrients and micronutrients it needs for good health.
Do you use fertilizer? Some plants do better with a more dilute feeding. Some directions will say to feed weekly or every two weeks, etc....but some plants may not be heavy feeders or smaller plants growing in larger pots can not use that much food. Most of the plants I have in pots are planted in good soil with compost and slow release fertilizer. They are pretty much okay unless they require a lot of watering due to heat and drying winds or if we have lots of rain. Then, I use 1/4 strength fertilizer every two weeks.
If I remember right, your area has had some very hot weather (temps in 90's and 100+) the past two weeks.....Oxalis for the most part tend to slow down when the temperature gets above 80 degrees, and plants in containers will slow down a bit sooner.
You may want to try planting a few in the ground where they get a bit of morning sun, but bright shade the rest of the time.
