The blacks are clogged on my Epson R800. Usually the print head cleaning utility works but this time it won't fix the blacks. I just used it a few days ago and everything worked fine. I've been using the bulk ink system without a problem for 3 months. I ran the cleaning utility 4 times. One of the blacks starts working but then gets clogged. I don't want to run the head cleaner too much and use up all my ink. I noticed all of the ink levels have gone down in all except the black. I checked all the tubes and made sure the cartridges are seated properly. What else can I do? Is it possible go get access to the nozzles at the bottom of printer head and clean them manually with alcohol?

update:
I discovered it wasn't the printer head, the problem was in the CISS. Unfortunately, I ruined a perfectly good printer in the process.