Also you said you have a pair of mini-harvesters collecting from Thr same planet in your home system. One miniharvester is more than enough to harvest from a planet in your home system. Send the second harvester to a different planet. A single miniharvester is even enough if it is harvesting from a planet in an adjacent system from you. Once the planet is 2 or more systems you need to use a full size harvester or cargoship