I'm not an expect on citrus, but I heard that adding Epsom salt really helps citrus. Add one tablespoon to a gallon. Also, an all purpose fertilizer for citrus does amazing things in my trees. In general, your tree appears to look quite healthy based off your pictures.

From the information currently present, and from others advice and my experience, those leaves look old and the tree is just getting rid of them.... Before they drop old leaves, they suck most of the nutrients from that leaf to feed others. I love biology and science lol :)

Your tree looks good. It should improve once it’s outside.

i would never use osmacote on an indoor plant .. ken

Ken, why on earth would you not us Osmocote on an indoor plant??

its made for use in a nursery.. where daily waterings flush out the bottom ....

osmacote tend to dump in 2 or 3 stages ... and then all on say one day ... when the temps and the moisture is right.. it dumps it all ...

and if you are not watering with flushing.. you might burn the roots ...

i would prefer to use a highly diluted water sol fert.. every time i wanted to apply such . ....

i would want to be in charge of the amount and application rate ...

i hope you didnt use much at all ...a little of this oor that.. rarely hurts anything ... but too many peeps think their plants are children.... that need constant and high feeding ...

and btw ... did you use the 4, 6 or 9 month release formula???

ken

some previous discussions of such:

https://duckduckgo.com/?q=osmacote+gardenweb&t=ffsb&ia=web

Ken, where did you get your information for"osmocote tend to dump in 2 or 3 stages ... and then all on say one day ... when the temps and the moisture is right.. it dumps it all ..."? This is counter to my understanding that it releases fertilizer slowly over a period of 4 - 6 months, depending the temperature. By the way, your link to duckduckgo provides links with too many websites for me to wade through them to find an answer to my question.

I use Osmocote Plus, at the rate recommended by the manufacturer, and Foliage Pro (1 1/2 Tsp/gal) about every other watering with no fertilizer burn problems.

Your tree looks fine, and I fertilize citrus with a mix high in nitrogen , as they are heavy feeders. Osmocote would not be my choice. Citrus are one of the few plants that I fertilize regularly, and to make things easy, you can buy 'citrus food' which is, no surprise, high in nitrogen.

Thanks for the replies all! It just struck me as strange that a bunch of leaves are coming off the tree.