Ammonia spike after adding live sand to 1 year old tank

I have been having issue with what appears to be green hair algae on some of my rocks and a purple/red algae on my sand bed since I setup this tank about 1 year ago. I have slowly been removing some of my current sand and a week ago I added new sand to replace it. I did not have a deep sand bed, it was maybe about 1" deep. I added 1 20lb bag in last Thursday which covered about 1/3 of the tank in about 1.5". I noticed about 2 days ago one of my soft corals wasn't open; I didn't think much of it but then yesterday I noticed my frogspawn was also not fully extended. I tested the water and my ammonia is between .5 and .8 using a Red Sea test kit. My main question is would the sand of caused this spike? I wanted to replace it sections just to avoid this scenario.

Also, should I try to do water changes until the ammonia goes away or will that just prolong this mini-cycle? I have Bio-bacteria and Vivid Aquarium cleaner which are both type of bacteria too help with this. Should I try dosing the tank with these?

Some information about my tank -

65 Gallon Red Sea Reefer, mostly LPS corals with a few soft corals and polyps. 1 clownfish, 1 trigger fish, 2 blue damsels, purple dottyback, and a royal gramma. Parameters- Mag- 1400 Nitrate- 2 Nitrite - 0 Ammonia - .5-.8 Ph- 8.0 Phosphates - 0

I do have a plate coral in the tank that is dying that i think may have knicked when doing a water change and it has been dying every since. It only has a small living section left. Would this cause the spike? Should I remove it? I read that it can come back at some point.

Thank you for any help!