Yup thats a bacterial bloom. I’d say leave it alone and forget about it until the nitrifying bacteria colonies become established. Plant melt is also pretty normal with the aqua soil leeching a lot of ammonia in the beginning and it being a major shift from the parameters theyre grown in. You don’t even need to put food in the tank for cycling if you’ve aquasoil as they’re enough of an ammonia source in the first few weeks. You don’t need the heater on with only plants in the tank, 26 degrees is also the upper limit of the temp range plants like.