The tomato plant has been developing yellow spots on all the leaves, as shown in the picture. I am not sure what might be causing it. I wouldn't assume nutritional deficiency as the compost is fresh. It got cold for a couple days in between but the weather is back in the high 70s. Could it be a pest infestation?

Please let me know. Thanks in advance.

I don't understand the point of the bottomless pot. 15 gallons is a good size, yes (though compared with the size of the leaves, the pot doesn't look anywhere near that large!) but the existing sides of the pot have no purpose (that I can see, anyway) except limiting root growth ... well, I spose it could also keep moisture where the roots are, as long as you're watering regularly or have an irrigation set-up (I do see the black plastic on the left of the photo, but it doesn't resemble the irrigation systems I'm familiar with).

The soil/compost mix you used in that container - which is never recommended for a container - is very likely low in many of the minerals but high in calcium carbonate - most all rockery soils are - and that CaCo3 interferes with manganese uptake by the plant. If there are no signs of any pests then I suggest some internet research into that deficiency.

There are many different tomato nutrient deficiency websites with photos that you can compare your plant to.

The simple solution is to transplant it into the ground which is rarely manganese deficient (not sure what the purpose of that container is anyway). Or if you are going to confine it in a container then use a proper soil-less container mix, one that also contains added soil bacteria so that your compost can be of any benefit to the plant. Compost provides no nutrients without an active soil food web to digest it to a form usable by plants.

Dave