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While I would recommend transplanting in fall or even spring, as long as you provide them with adequate water while they are establishing themselves, you can do so now. It also helps to make certain that all the roots are included when lifting and sometimes pruning them back will help alleviate transplant shock as well.

There are several factors that could be the problem. Pinpointing the right one can be difficult. However, here are some things to try: Check your soil conditions. Chances are this is a soil problem. How's your drainage? Is the soil staying too wet or too dry? Amending the soil with compost can help fix these issues. The addition of fertilizer may be helpful but will not solve the issue itself. Dig or poke around in the soil and check for signs of pests (such as grubs). Inspect the plants for pests as well. How much sun are your plants getting, etc.? Finally, check out the variety that you are growing. Many people do not realize that there are different types of black eyed susan plants available including annual, biennial and perennial types. Each variety has varying growth rates and heights. There is also a dwarf variety and this could be what you have.

This article has the information you're looking for, and more besides: https://www.gardeningknowhow.com/ornamental/flowers/black-eyed-susan/black-eyed-susan-flower.htm

It definately sounds like something has been nibbling its leaves. Exactly what insect is difficult to say as there are many that it could be, including slugs, caterpillars, etc. I would recommend treating the plant with neem oil, which is a safe and effective insecticide. Here is more information: https://www.gardeningknowhow.com/problems/pests/neem-oil-uses.htm

These articles may be helpful to you: https://www.gardeningknowhow.com/plant-problems/disease/plant-leaf-spots.htm
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