At this point your best bet is to add hydrated lime to the water reservoir. Use 1/4-1/2 cup and do this once. I would wait until you have fruit set though and perhaps skip it altogether unless you actually see BER. Did you use a commercial, peat based potting mix? If so odds are there is already lime in the mix. While the EB instructions call for quite a bit of lime to prevent BER with tomatos, plenty of people have skipped it and not gotten BER or gotten BER on a few early fruits and then not again. No worries, just have some hydrated lime on hand if BER becomes a problem.

You don't have to worry about stealing my thunder Al. Foliage Pro has an NPK label indicating 9-3-6. This is a 3:1:2 ratio. 18-6-12 is as well. 10-10-10 is a 1:1:1 ratio as is 20-20-20. The ratio says nothing about the 'strength' or 'potency' of the fertilizer, just how much of one nutrient is present in relation to another. Since Foliage Pro is 9-3-6 and ProTekt is 0-0-3 assuming they are both mixed at the same dilution (full, half, quarter etc) then the resulting ratio is 3-1-3. Mixed full strength the percentage is 9-3-9. One tip with the PT is do not mix it directly into the FP. It will turn into a milky goop (the label instructions indicate not to mix the two directly, but I had to try it to find out why :) Does this answer your question? Your other question is whether it would make sense to boost the potassium (K) higher. Well, it might in select cases, but for tomatos, according to the tissue analysis I have seen, the plant isn't likely to need or benefit from the extra except in a short window around the time the first fruit is ripening. After that the need for K actually drops slightly. Here is a link to a lengthy study on veggies and the macro/micro nutrients they use at different stages. I think you will find that virtually everything is suited to a 3:1:2 or 3:1:3 ratio fertilizer. Foliage Pro and Protekt fit this need nicely which makes it a very simple one (two actually) stop shop for container plant fertilization.

David, fertilizer doesn't need to be added at the time of seed sowing, ever. Once the seeds have germinated and the plants are growing is when container grown plants require supplemental nutrition. HOWEVER! I suggest that you read the label of your choice of potting medium carefully. Labels can have important information, even the label on a bag of potting mix. Your potting mix has fertilizer in it. Good luck with that product!

Couple of things - seeds do not need any fertilizer until they have developed to the point where they have their second set of true leaves. Seeds themselves are pretty much a fully self contained growing unit with all the stuff (technical term :-)) necessary to get them through germination and into the seedling state. That's when you need to start paying attention to nutrient needs. Also, if you read the label, your potting mix is already already inoculated with a fertilizer. It is also not one I'd highly recommend for seed starting. You don't need the ferts nor do you need the moisture control. And this is really Miracle Gro moisture control potting soil under a different label (Scotts = Miracle Gro), which tends to be overly moisture retentive without any moisture control additives! For seed starting, think very light and fluffy and sterile. I favor a 1-1-1 formulation of fine peat, fine perlite and vermiculite (and seed starting or rooting cuttings is the only time I advocate using vermiculite in a potting mix).