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.
Display Type: Analog
DIY Supplies: Woodworking
Name: soil PH tester
1 x 3 in 1 Moisture / PH / Light Meter Soil Garden Tester