If you decide to start growing a vegetable such as a cucumber, then it will be useful for you to find out what diseases of cucumber seedlings exist.
There is such a fungal infection as black leg. To reduce the likelihood of blacklegs, you can add wood ash to the ground before planting.
Very often the following situation occurs: the plant grows and develops normally, but at a certain moment it suddenly stops growing, may wither or die altogether. This can happen if you watered the seedlings with cold water. The fact is that the roots of cucumbers simply die off and rot from the cool water. If you put a glass of cucumber on a cold windowsill, the same will happen.
There is also such a disease of cucumber seedlings as mosaic. This is a viral type of disease, it appears on the leaves in the form of light spots, the leaves of the cucumber wrinkle. When the seedlings are still very small, it is almost impossible to cure it of this disease; the diseased plant must be removed.