If I understand your problem properly, you're wanting it to place wheat and tomato, yet lettuce is also infiltrating your farm?So, I just completed the glacial precipitator quest and unlocked the rest of the food-related quests. At first I thought "Oh, just toast? That looks easy". Then I saw the quantity. Let's just say I was in shock that I need that many. And that's with a mostly-automatic farm that I have (Basically it's a harvester, planter, fertilizer with no fertilizer in it at the moment and a pipe to a sludge boiler. The non-automatic part is that I still need to feed the steam dynamo).
Also, I've noticed that the planter, despite me using the filter to make it so it plants in this way:
WWW
TTT
LLL
(W = Wheat, T - Tomatoes, L - Lettuce), it's not planting any lettuce. Maybe I just don't know how machines work, I don't really know.
Finally, I've had a most peculiar occurrence: After a few minutes spent in the nether, all mobs except for the pig-faced non-aggressive enemies (I'm guessing imps) (And I guess and hellfish I expose) just stopped spawning. I was on easy, but I found that to be most peculiar. If nothing else, it made my nether resource gathering journey pretty much painless, allowing me to grab 4 stacks of soul sand, enough redstone ore to give me ~300 redstone and enough coal ore to give me ~4 stacks of coal. Oh, and about 2 stacks of iron and copper ingots worth of nether ore.
Do you have another planter within range of it?
(Within 13 blocks)
If yes, what is the range it is planting in? It could be planting in over that farm?