What are these black spots on white splotches appearing on my tomato seedling?

Question

Here are pictures of the infected leaves. I cut them off the plant as soon as I saw them today.

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Here are close-ups of the most infected leaf:

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What can I do to prevent this from happening to the rest of the plant?

Edit
I may have found the culprit. I found the what looks like a fruit fly right beside a new white patch. I am not sure if it was snacking or had just finished laying eggs. I am actually not sure if it was a fruit fly at all. Here are some pictures:

The first two are the bugs in action. Here is a close up of a bug I caught while cleaning the leaves with soapy water.

Can anyone confirm this is a fruit fly and that it is the bug responsible for the white mess?

Answer 1

This is definitely not a fruit fly as they do not damage leaves and the body of the pest is longer and thinner.

The original poster advises that the eggs of the pest are a different colour then a tomato leaf miner, my first identification. The most likely pest is the thrip as seen in this picture here. They are common, feed on a wide variety of crop and ornamental plants and the damage the larvae cause looks like a leaf miner. They also leave black "frass" on the leaves where they lay their eggs. This guide from the Ministry of Agriculture may help you.

For ornamental plants I have never been able to control thrips with or without pesticides. The eggs are inside the leaf and cannot be controlled with soap. The only solution was to destroy the plant. You may have success with removing damaged leaves, surrounding the plant with a fine mesh to prevent new adults from arriving and applying soap and water.