northernlights+lemon auto guerilla

i feel like the growth is going really slowly, it may be from the shit soil i was using, just the budget stuff from the local bunnings warehouse that has chunks of bark, mixed with daltons compost and scoria, i have found both of the lemon plants have weak stems specifically with lemon #2 the stem is unable to support the weight of the plant and it falls over, for this reason i buried the plant with soil up to the first set of cotelydon leaves, a temporary fix, i don't know why the stem is so weak, if anyone can help please comment below. other notes: i relocated the plants to a sunnier spot outside my house which gets about 6-8 hrs of direct sunlight and rest of the daytime it is covered in shade past few days have been cloudy no nutes also I'm going to move it out to the spot soon