All of the top leaves are like this. A few of the smaller bottom leaves show no brown speckling in the veins. The plant is also starting to shed the leaves with heavy browning in the veins.

Looks like Scale IMO, a pest problem common to house plants and difficult to eradicate. They are actually insects although they don't appear as such. Neem Oil spray helps but many recommend first cleaning the leaves with cotton balls dipped in a mix of rubbing alcohol and water 1 part alcohol to 5 parts waters. I have no idea how well this will work on tomato plants, no personal experience using it on them, since they are not normally grown indoors. You can Google 'Scale on house plants' for more info and lots of pics. Dave

Looks like Malibu Green to me. M. Teixeira is holding a large slab for us, which will go on our island, whenever the heck our house gets built. The stone is actually a serpentinite, with just enough talc to qualify as soapstone. It is much harder than soapstone, and pretty near indestructible. Also, it doesn't get oiled, just leave it as is. A short while ago, M. Teixeira had just a few small slabs left. They must have sold out, as I see now that the stone is no longer listed. The brown veins, btw, are iron deposits. Hope that helps.

Moving this thread from Citrus forums to Tropical. http://forums.gardenweb.com/discussions/3253262/guava-leaves?n=9