ok heres your problem.

dont think of weed, you know what ph you need soil needs too be so a littl;e research on plants requiring this range of ph will answer your question.

african violets etc etc etc google can be your friend.

indoor greenhouse, most will be using these for expensive delicate plants, show flowers etc etc.

sounds crazy your aiming too grow one giant tomato, you have done internet searches and plant would require bleh bleh ph soil for best results. ifthey ask more, you remove all trelles bar one and the plant puts all energy into this one trellis of fruit.