Best guess... not enough food; the grass is probably stealing most of the food you are applying. For the size of the tree you have a lot of fruit; I would probably remove half, if you want the tree to grow. More food, lees fruit and you should see better color; the rain is washing out Nitrogen, and that combined with what the grass is stealing equals yellowing leaves.

Umm, OP said tree is in a container. So, grass is not a factor.

But excess rainfall might be as it could have washed out the fertilizer.

Definitely needs food..mine was doing the same thing..

Myer lemon trouble

more than likely it's a zinc deficiency. I applied some regular citrus fertilizer a few weeks ago and the problem has since cleared up.

Good luck.

What was the brand of fertilizer? There are differences between fertilizers in that some that are meant for plants in the ground don't work as well in a container.

Also in my experience, most organic fertilizers do not work as well in a container. The organic fertilizers are raw materials, ie; blood meal, cottonseed meal, bone meal, etc. which relies on the soil microorganisms to convert the raw food to nitrogen, phosphorus and potassium and micro nutrients which the plant can then absorb.

Most potting mixes do not have a sufficient amount of soil microorganisms to do that converting, so the plant can't absorb the food.

I'd use a slow release food such as Osmocote Plus if I were you, especially as you're getting a lot of rain. It doesn't wash out of the pot nearly as quickly as regular granular foods. And the Plus formula is advertised to last 6 months, though with all that rain it may be more like 4 months.

Hi everyone! Yes it is in a cedar barrel container. I have been using a organic fertilizer and I will use BarbJP's advice. I will also reduce the fruit yield this year as I figured it was stunting the tree. Thanks everyone so far who have posted.