When you added the plants, you stirred up the substrate. This in turn, released NH4 (ammonia) into the water column. You have what is called a greenwater bloom. Harmless but will not usually go away on its own. The best method to get rid of it is using a uv sterilizer on the tank for 24-36 hrs and do a large waterchange to remove dead algae. Or you can do a 3-4 day blackout followed by same large waterchange (50%+).
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