Besides the crustiness, the edges are dry and there is a purple discoloration to the bottom of the leaf as well as some mottling from above.
If you have a hand lens 15x or better take a look under the leaves and see if you find any sucking insects. Thrips are tiny and often leave the leaf edges drying.
How old is this plant? The purple under the leaf may be because this is an older seedling that needs to be planted out or up potted and fertilized. Tomatoes are heavy feeders and they have large root systems, their growth should not be checked.
Happy gardening in Hawaii. Gardens are where people grow.