Fertilization Season Summary by Steve Jeppeson -

Below is a fertilization season summary submitted to Bigpumpkins.com - it has some good advice and guidelines for all growers:

Here's how the season goes here if the analogy would help.
Seed start to open ground - one week - no fertilizer.
The fertilizer ratios (when needed - depends on existing soil quality) are higher Nitrogen early (28-7-14, 20-20-20, etc). This we don't start for a week or more to allow the plants to acclimate & set roots. Some growers favor a "starter" fertilizer such as 15-30-15 (1 Tbsp per gallon) once after the first week.The high Nitrogen fertilizers would rarely last beyond 4 weeks.
At 5 weeks the plants would be between 4-6 feet depending on the weather. This period can seem agonizingly slow in growth if the nights & days are cool or cloudy.
Week 6-8 we switch to 10-52-10 to encourage flower formation. Vines shouldbe about 8-10 feet at this point. This might be 2-3 weeks at most.
A week or two prior to fruit set we eliminate all fertilizers to avoid failed pollinations. Too much Nitrogen at this time is disastrous.The goal here is to have a fruit set in the 8th or 9th week after setting the plants out. Thus the vines will be about 14-16 feet (5 meters).
For the 3-4 weeks after fruit set we also don't use any fertilizer. But once the fruit areFirmly established, we then switch over to the higher potassium fertilizers such as13-0-46 Potassium Nitrate or similar.
All of the rates we use here (if at all) are greatly reduced from label recommendations. This is because the soil is already rich with organic matter (19%) & manures.
All doses are singly & per week if made at all. A lot has to do with how the plants look. Healthy green growth is a good indication to skip a week. Lighter green or slow growth with smaller leaves indicates a need for Nitrogen.
All of this is based on local soil conditions which are determined by a comprehensive soil test performed by a commercial soil testing laboratory.
I suspect that day time misting & shade cloth might be in the future for you?Actual water use would range between 200-250 gallons per week for a 400 sq ft plant minus real precipitation. But sandy soils in high heat might require more.
Is your irrigation water all affluent from the house? If so, has it been tested to insure its use isn't causing a problem?
There is also the chance that Nematodes or a soil borne vascular disease could be slowing down the growth of your plants. Steve