Try some vinegar to lower the PH of your wash, but I bet the issue is your light source. Google the wavelengths of halogen. Very little of it is in the UV range. When there is no sun, I use a single 15w BLB. Covers up to 8x8 inches and gives me exposures of about 1 hour with double-coated traditional chemistry. Also, overcast days are the best for printing cyanos outdoors. You might have more sun than you think you do.