There are many benefits to using leave-in conditioner with one of the main ones being to provide continuous moisture and protection to our hair. If your regular brand it isn’t working as good as it did before, it possible that you may have a hormonal imbalance. Generally, when this happens, or when women are under a lot of stress, it causes depleted levels of vitamins which turn ha been known to cause hair loss or frizzy hair.
I would suggest maybe a bit of diet/lifestyles change (after carefully evaluating what changes may be necessary) and incorporate foods that will help restore some that lost nutrition. You can read more about which leave-in conditioner brands are best in this post here:
https://www.samplehime.com/bath-products/conditioners/good-for-your-hair/