Just an opinion

Changing the nutrient dosage can be tricky , what you did by adding more Part A is a good way to go as it brings more N ( 3% in part A ) but I feel like a cal mag bottle would be more interesting as your part A contain only 0.70% of MgO but 2.20% of Cal so you'll bring a small amount of MgO compared to the Cal so maybe you'll get a MgO deficiency in the futur. If you wanna change something in your setup it should be the humidity level as ot that satge your should be around 60/70% and not 38% which is too low so you can buy an humidifier or you can add a bucket of watter in your tent ( a glass is enough ) and let the heat create humidity

Get an EC / PPM meter, it will take the guessing out of feeding. As for watering, learning how much to water comes down to experience, if you are unsure, lift the pot to judge how much water it has, when in doubt, do not water, at worst you will force the plant to develop a stronger root zone; you can wait until the plant wilts a little. Anyway, for a plant that small, i would not water more than a glass of water.