As the previous poster said, it doesn't have to be exactly EASY, and it doesn't have to be exactly 4 hours. If he isn't hungry before then, keep feeding every 4 hrs. My dd was a 30 minute napper until she was 6 months old, so we had EASAE. I have had routines of 2.5 hrs, 2.75 hrs, 3 hrs, etc. EASY is a guideline to get you on the right path. I feel that it is a method to help your lo establish comfort in a routine so that he/she knows what to expect. Also, it is a tool to help your lo with independent sleep rather than relying on a feed and other accidental parenting pitfalls to fall asleep.
He is probably going through a developmental phase that is affecting his naps, and he will more than likely return to taking 2 longer naps in the following months. However, as mentioned, he may not need much day sleep if he seems to wake happy and be content through A time.