it is not normal after 12month of use to have such problem when tubes should run at least 10000h.
It's always normal for tubes to fail.
1 hour or 5000 hours, anytime for no good reason. The dark side of tube amps is that they use tubes! But the sound and the overall ownership experience is well worth it.
You can minimize the disappointment of the inevitable failures by being prepared. Having spare tubes, fuses, and other parts that are known to fail will usually make fixing it quick and easy. Your amp is designed to protect itself from the expected failures like tubes, so you can expect repairs to be fairly simple that you can do with help from mfg by phone or email. But without parts on hand it's much less fun waiting with no music.
Every tube amp and preamp I've used has had at least one tube failure, some had several. Almost all were very easy to fix. Waiting for the parts to arrive was the worst part. Once I learned to stock parts I was much happier. The mfgs always helped me by phone and email to fix it myself. Only once did an amp require shipping back for repair, but when it arrived, they couldn't find any problem! Tube amps are frustrating, but the unique sound is worth the aggravation, and you can minimize the negative feelings by being prepared.