Help Titrisol!!

I followed the recipe for Caffenol for 500ml as follows:

500 ml of water (for 120)
1 gram Vitamin C
4 teaspoons washing soda
8 teaspoons instant coffee

I mixed the Vitamin C first till completely dissolved (@ 75 degrees), then baking soda till completely dissolved, then coffee till dissolved.

And tried to develop 2 rolls of 35mm. It was fomapan 100 exposed at asa 64. Agitation 5 sec. (gentle) every minute. Total dev time 30 minutes at 75 deg.

I got the absolute faintest, barely there negs. The film leader was a pale grey.

Any suggestions what I did wrong? Too many rolls? Temp to hot?