Photos please. Really can't help you unless we see the trees, how they're planted, etc. Also, we need to know how much they are being watered, fertilized, how much sun they receive, etc. It may be nothing at all, or, we may be able to make suggestions on care for you, but we need a little more info to be able to help you out.

Patty S.

Thanks Patty for the reply, I've included one image, both plants look similar. They get 4-5 hours sun a day, fertilized(Osmocote) in March, due for more in July. We have had regular rain since summer so I haven't had to water. It just seems strange that these two do little compared to the other two citrus.
Tony R

Nitrogen Starved

Wow, I would check to see if they are too wet in the root area. It is possible you've got root rot going on (Phytophthora). I would make sure you've not got soggy roots, first off. I would also consider treating with AgriFos (Phosphorus acid). 2 Tbsp. in 5 gals. of water. Treat now, then a second treatment in 6 weeks. Then, once every 6 months. Since you're fertilizing, yet the tree looks extremely chlorotic, I am suspecting your tree is struggling to absorb nutrients due to root compromise.

Patty S.

Thanks Patty and Ryan I'll try your suggestions.
TonyR