It is difficult to say for sure what is causing the symptoms from the images alone. The symptoms look a little more like insect damage to me, but insects are what spread the disease too so there is a chance the disease is present. Here is a link to some information on milkweed yellows, which is a phytoplasma spread primarily by leaf hoppers though aphids are also know vectors - https://monarchjointventure.org/blog/what-is-milkweed-yellows-phytoplasma. The article discusses some of the symptoms and management. Unfortunately, there is no control for phytoplasma diseases other than controlling the potential insect vectors. Once the plants have the disease it is best to discard/destroy the plants. 

You can continue to grow them to see if other symptoms more characteristic of milkweed yellows appear or you can take samples to the Oklahoma County OSU Extension Center (https://extension.okstate.edu/county/oklahoma/) to be submitted to the disease lab for diagnosis. The best way for early detection and confirmation of presence of the disease is diagnostics through the disease lab.