As im looking through your diary I dont really see any of the classic signs of over watering which is good . A plant can grow slowly for a few different reason but the main reason I can think of based on the stats in your diary is that your day time temps are abit to low I would firsty try and raise them above 23 c and no higher then 28 c I would also suggest to raise your substrates temperature because being at 20 degree's your root system will absorb the water more slowly which will result in slower growth . All in all your plants look great I would just fix the temperatures a bit and your plants will rock and roll and night and party everyday ! I hope you find this info useful . -Happy Growing!