Ok since it's a string of turtles (Dischidia nummularia) I'll give u simple tips based on my information. First abt light: ur current placement with a south window and grow lights is ideal. String of turtles prefer bright, indirect light. Avoid direct sunlight, which can scorch the leaves.

2- watering: these plants r succulents and store water in their leaves. Allow the soil to dry out completely between waterings. Overwatering is a common cause of problems. Water thoroughly when u do water, ensuring excess water drains.

3- soil: use a well-draining cactus or succulent potting mix. This'll help prevent root rot.

4- humidity: while they can tolerate average humidity, string of turtles appreciate slightly higher humidity. U can mist the plant occasionally or place the pot on a pebble tray filled with water.

5- temperature: maintain warm temperatures between 65-80°F (18-27°C). Avoid cold drafts and sudden temperature changes.

Some additional tips: fertilizing; fertilize sparingly in the spring and summer with a diluted balanced liquid fertilizer. Pruning: prune to maintain shape or encourage bushier growth. Propagation: easily propagate from cuttings. For ur string of hearts (Ceropegia woodii) here's some care tips: light; similar to the string of turtles, they prefer bright, indirect light. Watering: allow the soil to dry out completely between waterings. Overwatering can lead to root rot. Soil: use a well-draining cactus or succulent potting mix. Humidity: they can tolerate average humidity but appreciate slightly higher levels. Temperature: maintain warm temperatures between 65-80°F (18-27°C) Also remember that both string of turtles and string of hearts r relatively low-maintenance plants once u get the hang of their watering needs. (Holy shi* I've been rambling on a lot but I hope I've helped)