Just a bit of brainstorming first:

1 What is it in your environment that is helping this stuff propagate?

2. Have you tried neem oil? I've heard that is effective versus fungi.

3. Are you sure it's not a nutrient deficiency? Because the fungicide spray is not working according to you.

I'll consult my nutrient problem solver tonight to figure it out and get back to you.

I use a continous drip irrigation system which may have helped it propogate, the top surface probably evaporated water which caused moisture to accumulate on the leaves. I haven't tried neem oil I am going to buy some though. I am pretty sure it is not a nutrient defeciency cause I have already done reservioir changes, checked pH and added a micronutrient supplement. The fungicide sprays and most fungicide treatments are preventive and actually not really that effective.

What are you growing? Basil tends to get these concentric spots - it isn't fatla and can be controlled by simply removing the affected leaves. It tends to be temporary.