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Yes you need a 10-10-10 complete fertilizer one pint equals 1 pound granular fertilizer spread water into soil once a month for 3 months. Study pruning for next 3 months you going need it tree rebound in about month.
The link below shows all disorders a peach nectarine and plum all same.

Here is a link that might be useful: Peach leaf disorder

I had that too last summer. I could be the curl leaf.

Hard to say for sure if there is anything wrong. At least not to the point of requiring any special action on your part. Check out the Backyard Fruit Tree Basics video on youtube. At 9:44 Tom Spellman talks about what to do if you think you have a problem.

In general, Dave Wilson Nursery recommends GRO-POWER FLOWER 'N' BLOOM 3-12-12 and mulching heavily. Most of the local nurseries here in So Cal carry Gro-Power products.

Here is a link that might be useful: Fruit Trees in Bloom 2013

Confirmed. It was nitrogen deficiency. Few handfuls of fertilizer later and they are growing again and deep green

I would like to know if you know why my nectarine tree did not bloom this year. I live in zone 5B.

Which pretty much shows why 3-12-12 is not a generally recommended ratio for fertilizing peaches. Can't understand why that would be recommended except on sites with 4 plants to a hole where a lack of P has been diagnosed in soil tests. Low N would be to discourage excessive vegetative growth.

Commercial growers here usually use a high N fertilizer for peaches with about equal K and no P. Blindly adding P may disrupt the nutrient balance by tying up other essential nutrients.

Because P often washes into waterways and causes environmental problems it has been removed from most home lawn fertilizers. Trees usually do fine without much of it in the soil because of mychorizal relationships.