It would really help with isolating problems with a little more data to work with. Here are a few reasons why leaves turn yellow ~ without spots. Non Disease. Overwatering Cold Pot Bound Nutrient Deficiencies Air polution Old Age Insects Nematodes Root Rot Viral Diseases. There are over 1,100 plant diseases, Where you are from? State is usually close enough IE Coastal US and southern border states, A greenhouse whitefly sucking on your leaves will make the leaves yellow. Per my map, these bugs don't live in the Central Plains States. If you are in the Northeast, Night temps into the low 50's cause problems. The more data you can give, the closer some folks can get to your problem. Byron