I really think you are underwatering a bit based on the separation of the soil from the edges of the pot. When you water what is the drainage like, is a good amount of the water draining through or when you water is it just absorbed....a good amount should be draining back out. Those look like pretty good size pots. I would use a half gallon pitcher that you can get anywhere fill up the pitcher and water all three evenly from the pitcher, most of it should drain off but it will be a good healthy drink, I water every other day based on this method.