The roots are dying so no fertilizer is going to work unless you flush out that mix or use a whole fresh one and once the plant starts to recover, you fertilize as Steve suggested. If you have access to rain water or bottle distilled even better to use unless you change the whole mix including in the root ball. You are just going to further damage the roots with fertilizer in that mix. Flush, flush, flush)

Highly unlikely you have Greasy Spot. You see that in the high humidity states with outdoor citrus. Unless you live in a steam sauna, that would be just about impossible in your house :-) I suspect we have low light issues, possible watering issues and either soggy soil, or hydrophobic potting mix (not absorbing the water). You don't mention what potting mix your tree is in, that helps us to know what's going on in the root system. You don't mention what fertilizer you're using or how often you're fertilizing. The browning at the tips can be due to watering issues or over-fertilizing or fertilizing with the wrong type of fertilizer (causing nitrogen burning due to a build up of nitrogen by products - biuret). So, more info, please on light, fertilizer, potting mix, watering, etc. And, to load multiple photos in one message, upload all your photos to Photobucket.com (fix your orientation - if you're snapping photos with your iPhone, take them in landscape with your volume buttons facing down), then copy and paste the HTML string into the body of your message. You can paste in all the photos' HTML strings, and they will then ALL appear in your message. You'll know you've done it correctly as they will all appear in your message when you click on "Preview" button to preview your message. Patty S.

I agree with Jean. I would use a very well draining mix. I use EB Stone's Cactus Mix, but there is also a good recipe on our forum to "511" mix or "gritty" mix that you can search out. Definitely needs to be repotted, and the roots straightened out if you see they're circling in this small pot. Also, I would consider switching fertilizers. 4 fertilizer applications a year for a container citrus is not nearly enough. Fine for in-ground citrus, but not for container citrus. I would consider using Dyna Gro's Foliage Pro, and use 1/2 strength with every watering. And, I would also supplement with Osmocote Plus (it must be the "Plus" formulation so you have the best NPK ratio along with all the micros, very important). Your tree is in bad shape. I would expect after re-potting and correct fertilizing and watering that you'll see these old leaves drop, pushed out with new flush. Patty S.

I would switch to a more appropriate fertilizer. This particular fertilizer is very high in N, and nearly all from a Urea N source. You're seeing biuret build up and burn. Most container citrus folks on the list have found that Dyna Gro Foliage Pro fertilizer does an excellent job without burn, and with a better NPK ratio (and better N source). Also, you may want to consider a different potting medium as well. If you search for "511 mix", you will find a great recipe for an indoor citrus potting medium. Citrus do not need an acidic environment - not sure how this misconception started and continues to circulate. Citrus actually prefer a rather neutral environment. If you tap water is extremely alkaline, you can consider acidifying it with a little vinegar, but citrus do not need fertilizers designed for "acid-loving plants", as they do not fall into that category. Patty S.