What you have is good. Citrus likes it acidic and 6.0 is about perfect. So, the water Ph is OK. The soil Ph is good. Your plant food is good. The only thing left is your watering, watering times and watering technique.
Too much water will NOT hurt a plant if it can drain. Water doesn't damage a plant, the lack of oxygen does and too much water for too long of a time, forces out the oxygen that goes to the roots. But root damage doesn't happen over night. It takes time for root rot and other diseases to grow so this is why adequate drainage is so important. Knowing how and when to water a plant is very important. Watering a little but often is not good. You should water a plant until ALL of the soil is wet. When watering seedlings pick up the container before watering and feel how heavy it is. Then water until ALL of the soil is wet. You should see standing water in the container. Then pick it up again and feel how heavy it is. When it feels light it is time to water again. The watering technique for seedlings is also important. Watering should be done from the bottom up EXCEPT when applying fertilizer. I use a plastic dish drain pan to water with. Fill it about half full and place your plants in it. When the top of the soil is wet remove them. Only when applying fertilizer do you water from the top.
