I would caution you seeding into soil that has had high impact synthetic fertilizers applied to it. Seeds carry within them all of the nutrients required until they start setting their first true leaves. High potency synthetic fertilizers can easily burn the roots of young plants and they also increase the level of salt in the soil, tying up vital moisture, micro-nutrients and calcium. If you can't tell, I am not a big fan of high powered fertilizers, and I tend to use slow release organic sources.

However, if you wish to use them, I would suggest you seed into a relatively infertile soil. I usually scoop out a couple of handfulls of soil and replace it with potting mix, then seed into that mix. Once the seed sprouts and starts to grow leaves, apply a balanced liquid fertilizer (like 25-25-25 type) and water into the roots. You can also apply it as a foliar spray, diluted by about half in a spray bottle. As the plant grows to about four or five good leaves, start applying the granular fertilizers in a ring about 12" from the base of the plant, worked into the surface of the soil, then watered in. This one should be heavier on the nitrogen, such as 20-5-5 or so, or even 40-10-10 if you want something more powerful. Repeat this fertilizing "ring" as directed on your label. Gradually make the change to your 9-23-30 when the plant starts to show signs of flowering.

Seems like alot of babying, but you will need good, healthy growth initially to fight off the eventual arrival of the SVB, cucumber beetles, squash bugs, or all three.

Hope this helps.