Can you post pictures?

Also, are they in pots or the ground?
Have you fertilized?
If so, with what? And how often?

Jean thank you for asking,they are in pots in my small outdoor greenhouse.I have not uesd anything except superthrive which is not a fertilizer but they are in miracle gro soil.I have not yet learned how to load pictures on to my computer sorry.Can you help me?

Containerized plants require regular fertilization (at least every other week) with a suitable, water soluble fertilizer such as Miracle Grow powder that is mixed wit water (and many others), the MG soil doesn't do this. Never believe the bags that sometimes say 'feeds for x months'. They don't have enough fertilizer for veggies.

I would also shake the plants and see if any whiteflies... I have all my plants in containers or raised beds but left 1 in a lean-to greenhouse to do a comparison... it was nice a few days ago but now has many yellow leaves. Shook the plant & saw a bunch of whiteflies emerge!

I agree on regular fertilizing or at the very minimum, a couple tablespoons of time release Osmocote 14-14-14 or Miracle-Gro Shake & Feed for Roses (9-17-9 I think) at planting time, plus supplements.

thank you everyone I will give them some mg and see what happens

Organic fertilizers work too. Some are liquid and have immediate effects. Some are slower for gradual feeding. Or you could use a compost tea. It's hard to go wrong with that.