Have you just filled the tank with water or set it up? Two of my friends have used manado and found it quite light when planting. If you search on this forum you'll find posts about it. It might be something to consider if you've not opened the bags yet.
https://www.ukaps.org/forum/threads/jbl-manado-too-light-does-it-settle-down.42114/
Its setup.
I wish I saw this before, that Manado is rubbish - fish farts near it and it will be like a sandstorm. soon as there is any agitation its moving, sooooo light. I hope it does settle down over time, plants are indeed a nightmare to keep in.