Dosing schedules can be pretty flexible, you just need to make sure the plants have what they need at all times. The rate of uptake is going to be dependent on the amount of light and whether you are injecting CO2.
I like the Seachem line of ferts but for a large tank they are way too expensive, you are paying mostly for shipping water and for the bottle. There are only a few cents worth of ferts in each bottle. Suggest you look into dosing dry ferts which are dirt cheap.
I too, have a 90 gallon tank, pressurized CO2, 4 x 54 watts T5HO and currently dosing Seachem's line of ferts. I'm not that strict with the dosing schedule and like the previous person who commented here, I just make sure they get the right amounts they need. I hardly dose nitrogen as my nitrate levels are already between 20-30 ppm. I test for phosphate and dose accordingly coz the tap water already has some levels of phosphate. I dose potassium, iron, flourish, & flourish trace twice a week each. I dose excel twice a week as well eventhough I'm running pressurized CO2. Just make sure you dont overdose it and even if you dosed half the amount it's OK too.