It could be with your soil, and so, what you need is this 3-in-1 moisture, pH and light meter with easy to read scale.
Your plants never need fear that you're going to mistreat.
It is easy to use and scientifically accurate measuring device.
Needing no batteries the prongs measure the moisture and pH content of the soil from root level and determine whether your plants are ideally situated.
With regards to their positioning.
The moisture meter works with all soil types and is suitable for use in or outdoors - simply place it in the soil, set to the setting you wish to measure and read the scale.
3 functions in one compact meter - measure the moisture and pH content of the
soil and the environmental light
No need for batteries
Easy-to-read scale indicator
Incredibly simple to use - just stick it in the soil!
Works with house and garden plants
Item size: 290*49*35mm
Display Type: Analog
DIY Supplies: Woodworking
Name: soil PH tester
1 x 3 in 1 Moisture / PH / Light Meter Soil Garden Tester
Yogatada 3 in 1 PH Tester Soil Water Moisture Light Test Meter for Garden Plant Flower Green B07RJX7JZM