The dosing seems a tad (way) off. Check out this
online fertilizer calculator.
Using the full 20 gallons (ignoring substrate, hardscape, plants etc.) this is what it recommends for a daily dose of 7ml (see below; teaspoons are close approximations to actual weight per teaspoon).
(946ml is = 32oz.)
53.384 Grams of KNO3 mixed in 946ml (1 teaspoon)
8.796 Grams of KH2PO4 mixed in 946ml (1-1/2 teaspoons)
72.962 Grams of K2SO4 mixed in 946ml (11-1/2 teaspoons)
31.337 Grams of Plantex GSM+B mixed in 946ml (7-1/3 teaspoons)
->Assuming plantex GSM+B is your trace. Mix this separately from the others. It can precipitate otherwise.
** A daily dose is alternating days. Macro nutrients one day then trace the next.
Below is what you added versus what is recommended to 946ml dosed at 7ml/dose
Your dose vs Recommended dose
KNO3 15.6 grams
vs 53.384 grams
KH2PO4 69.6 grams
vs 8.796 grams
K2SO4 19.2 grams
vs 72.962 grams
The algae may be caused from a nutrient imbalance. However since it is new you can expect to see this brown algae. It is called, among other things, "new tank syndrome".
Below are the weights of 1 teaspoon of each nutrient you are using. Check my math since I did it in a hurry.
KNO3 1 teaspoon = 5200mg (5.2 grams)
KH2PO4 1 teaspoon = 5800mg (5.8 grams)
K2SO4 1 teaspoon = 6400mg (6.4 grams)
Plantex GSM+B = 4300mg (6 grams)