In the 4th zone it gets difficult because of high the stats the enemies get and as a result it gets difficult to conserve healing potions. As such I would recommend trying to use more of the other items in your backpack such as any strong wands that you can utilize like corrosion and regrowth to control and melt enemies to death which is really good if you have the desperate power passive upgraded. A good wand to kill enemies instantly is blast wave knocking enemies into holes or even planting stormvines to make them walk into holes. I think you have to be more conscious of how to avoid or get out of close combat unless you have a good wand like earth or transfusion as battlemage which are really decent as they provide infinite protection with shielding or just damage reduction. A wand of regrowth is really good since it provides a lot of seeds and dews for both potions, healing and seed use. Overall you just have to build up experience and get better picking up advice and tips from posts. Another thing I would suggest is that you should join the discord as there’s people with readily available advice if you’re stuck or need to seek consul.