I planted tomato plants last year...

There is no nutrients to supply to the plants when lava rock is used.

I always use mulched leaves or cut grass for my vegetable garden with excellent results. I would never use rocks, as Janet stated above you get no nutrients from rock and they also can collect an awful lot of heat when it is sunny and hot. Change what you use and see if that makes a difference this year. Leaves and grass are free and can be worked into the soil next year to beef up your soil.

check with a nursery - some types of tomato do better in some location than others. if the lava rock is your only place to put the tomato- containers might be an option.

Those tomatoes didn't know that red lava rock was there, except some contend the red reflection will make the maters more red. Don't replant tomatoes in same place as last year..plant them DEEP (2-3" above dirt) best to have soil tested but use a good balanced fertilizer if you don't, work into ground, put 1T epsom salt around plant & in hole when planting. mulch well, water on regular schedule 1-2x a week, early morn. is best, use a soaker hose if possible, don't spray water over plant. If you're up north, don't plant until after mid-may, tomatoes don't like warm,cold,warm,cold nites...they're definitely warm weather plants.

Make sure that you're planting them in a different place from where you planted them the year before!

Thanks to everyone who replied back about my bad tasting red lava rock tomatoes. Received good info.