Yeah, pretty close. Give it a little while to settle down. Then you can add a few more platies or maybe some endlers (males only would be my suggestion, NO FRY!

). I wouldn't add more cories as your bottom would be too full.
You can add a few more fish than the "inch of fish per US Gallon" rule, but you need to do bigger more frequent water changes to ensure that things stay in check. We use nitrates as a gauge. You want to keep your nitrates as close to 20-40ppm above your tap water as possible. If you feed lightly, keep up with the water changes and stay focused on your fish for signs of stress, then you can get away with a bit more. But, generally, this isn't suggested for beginners.