I have yellow leaves on the bottom of my dianthus plants?

Question:

Answers:
This could be a few things. The main one is not enough nutrients especially nitrogen. Quite simply add some fertilizer. The other one is ..Plants can suffer from bacterial, viral and fungal attack just as we can ourselves. The organisms themselves (pathogens) are different, but at the microbial level the infection is much the same since one cell is as good a host as another. No matter which part of the plant is attacked the effect is usually to weaken or kill it. By infecting the leaves the plant's ability to produce its food is reduced. Some pathogens block the vessels in the stems which supply the leaves and by attacking the roots, the uptake of water and nutrients is reduced or stopped completely.
When a plant is attacked by one of these microorganisms the damage caused provides an opportunity for the others to get in and it is the combined onslaught which deals the final blow. Also if it is under stress, such as through drought or poor nutrition it is more susceptible. Try giving some fertilizer first and see if the plant picks up. Good luck