First from your probable location I would suspect you soil is on the acid side. If that is true then a Bray, or Mehlich chemistry is appropriate and then you soil test should be in the 30 ppm P range. At 15 lbs P₂O₅ to change the soil test one (1)ppm P we are talking about 200 to 250 lbs of P₂O₅ for a level that will be close to 100% of potential yield and/or where there is less than a 20% probability of a positive response to added phosphate. So no you wee not applying too much phosphate. You were probably close to being barely enough.

The potassium at 100 ppm K is probably a little low, unless your soil is really sandy, and a CEC in the 5 to 10 meq/100g range. In that case you will want to apply all your fertilizer in split applications. Possibly every 20 to 30 days. Most Labs consider 150 ppm K to be the level that has sufficient potassium that you do not require annual applications. If you have a heavy clay soil then 300 ppm K probably is deficient!

There are a few soils in this world that is so fertile not to require fertilizer for a few generations. Eventually though someone will have to pay for fertilizer. Here in CenTex a rule of thumb is there is $30 of fertilizer in a round bale of hay. Some pay for the fertilizer now and some put the cost off to a later date. Someone some time will have paid or will have to pay the bill.

Now to liquid fertilizers, phosphate mostly. Thee is some data that tells us if we deep band 10-34-0 there will be enough better production to pay the extra cost for material and application. The reason for this is the broadcast phosphate will become tied up in the soil by aluminum or calcium, depending on your soil. This is thinking short term annual needs. In most soils the phosphate will eventually become available. A rule of thumb is 20% of the phosphate you apply this year is available to the crop, this year. Then every succeeding year 20% of the applied plus 10% to 20% of the accumulated residual is available, that year. The kicker is I do not know how much of the accumulated phosphate will show up in a soil test. Probably not much. The solution is to keep records and know how much you took off and how much has been applied. In truth a phosphate analysis is an index and not an quantitative analysis.

So the 8-18-18 may be just what your crop needs for a pop fertilizer. Than again maybe not. Try some on a limited bases, cross check the production and also use a tissue analysis.