I would recommend you cut back on feeding spinach to once or twice a week.
Spinach and Parsley contain oxalic acid which binds to calcium, blocks the absorption of calcium and puts stress on the kidneys.
Too much oxalic acid can also cause poor blood clotting and convulsions in birds.
Other green leafy vegetables you can offer include:
fresh beet greens
fresh mustard greens
fresh turnip greens
chickweed and dandelion leaves (ensure they have not been chemically treated)
Please take the time to read through the Site Guidelines, the FAQs, the Budgie Articles and all of the Stickies located at the top of each section of the forum.
Truly, the very BEST advice anyone can offer you is to take the time to read ALL of the stickies throughout the various Talk Budgie forums as well as the Budgie Articles we have posted. These are great resources for Talk Budgie members and have a wealth of reliable information which will assist you to learn the best practices in caring for your budgies for their optimal health and well-being.
Most basic questions you may have are answered in the stickies and budgie articles.
As Cody asked -- did you get the antibiotics from an Avian Veterinarian or an Exotic Pet Veterinarian who has experience dealing with small birds?
What is the specific antibiotic and why was it prescribed?
As indicated previously: The key to a healthy diet for budgies is much the same as it is for humans and other animals. You are best to serve foods in moderation.
Twice a week is sufficient. There are many other things to offer your birds.