Hello and thank you for posting :)
The reason why you no longer can add vegetation can be related to many things including computer specs.
Same for the lights. I would need to know your computer specs and see the file so that we can help.
I suggest that you log a bug using the "contact us " button and share your file with us with your computer specs.
A support agent will get back to you with a workaround or a bug confirmation.
Thank you
MC