Answer: Without knowing the specific plants, it is a little difficult to make recommendations. However, for the first plant, the brown tips can be a sign of underwatering or drying out too soon due to needing repotting into a larger pot. This is plausible since it began to do better afterwards with healthy new growth.
Some plants will develop brown tips in reaction to chemicals in municipal tap water such as fluoride. (Use rainwater or bottled water to water.) Sometimes fertilizer salts accumulate in the potting mix over time and cause brown tips as well. (Leach the soil by watering heavily, allow to drain, and repeat in quick succession.) Some plants will develop brown tips in reaction to lack of humidity, something to consider, although more common during the winter heating season when our indoor air is so dry. Some plants will naturally lose their older foliage as new foliage develops, so what you are seeing might even be normal.
In any case, once browned the tips will not turn green again, so you can trim them off. The cut edge will probably brown as a result of being cut, so sometimes it is just as well to remove the entire leaf all at once depending on how it looks to you.
The clover type plant might be an Oxalis of some sort. These generally have a dormant period when they dry up and die back to rest, then regrow. When this happens, however, the foliage usually dries up rather than just collapses.
So, I suspect you may be overwatering. Overwatering can lead to foliage loss and crown or stem rot problems, as well as root or tuber problems. The moisture holding polymers in the soil mix could contribute to this because the soil is treated to stay moister longer. This means you need to water less often than you would with a polymer-free soil mix. Too, oxalis need a very well drained soil mix, often with coarse sand or perlite added to it, rather than one that holds extra moisture.
Oxalis also needs bright light (indirect light will do but it should be bright), so it may be a combination of overly wet soil and lower light levels. Finally, some types of oxalis grow best in cooler temperatures while some do fine in heat; a cool lover might collapse of kept outside when temperatures are very high. I hope this helps you trouble shoot.
Q&A Library Searching Tips