Bonsai of Watermelon Automatic

After germination the plants stretched quite a bit, so I: - moved them outside to have lower night temperature (14°C instead of 22°C) - added a cold (4000K) grow light (LED full spectrum spot light, 575lm, CRI 90) to increase light exposure from natural sun to 16h/d I measured the soil pH (which was supposed to be 6.4) with a calibrated probe and found out it is more like 7.0 so I: - started to give them a few drops of very low concetration rain water + nutrients solution (2.0-0.9-1.4 N-P-K) + a couple of drops of lemon juice to lower the PH On day 11 it rained a lot so I: - moved the plants back inside lo let the water saturated soil dry out a bit. On day 12 I found some aphids and a leaf miner so I - sprayed a 12.5 mg/l solution of Deltamethrin