Brown spots/tips on leaves (pic inside)
I posted a while back about my mystery South American citrus, which I'm starting to think may be a variety of Citrus aurantifolia Rutacea (aka Mexican or Key Lime).
I have three of these seedlings which I've been growing indoors for just about a year.
Two of the seedlings are in identical plastic pots (holding about two cups of soil). One of these two has had problems with brown spots on the leaves, as well as dry, brown leaf tips. Leaves also drop every week or two, some of which have brown tips, some of which just have a couple brown spots. The second of these has perfectly healthy leaves, but the new buds turned brown and dried up many months ago, so it has not had any growth in a long time.
The third seedling has been growing in a smaller pot, as it seemed genetically dwarfed to begin with, and is healthy but much smaller. Actually, I believe it was one of two seedlings that came from a single seed (I gave the other plant to a friend).
Growing conditions: All three seedlings are growing in a window in my bedroom that gets only a few hours of direct sun in the morning, under a supplemental compact florescent grow bulb. They are planted in plain old Schultz potting mix, which was all I could get at the time I sowed the seeds. I realize they should have something better-draining, and I'm planning on repotting them today with a better mix. I water when the top inch or two of the soil gets dry to the touch. In terms of atmospheric humidity, I have a cheap little gage (sold for animal habitats) that reads about 55% relative humidity right now.
I've done plenty of searching through pervious posts on the board, but I'm still not sure what the problem is. I'm attaching pictures, which are from my camera phone, as my real digital camera is having power problems.
Any help would be really appreciated. These plants have strong sentimental value for me.
Here is a link that might be useful: Picture of dropped leaf