Horse breading not the same as retail?

just bread two tier 7 level 30 horses and got a tier 4 horse. I thought it could only go one level below like a tier 6. Please inform me if i am wrong but this is potatoe.

 

Yes it's not the same as retail. You are not blessed by RNG and got unlucky. That happened to me last time when I was on training professional, when I got to master I never had bad luck on horses lowering tier via breeding.
In fact, I almost always get gold icon (coarser) horses.
Just be patient and you'll get the right breed. Also, as much as possible always breed on T8 Male. As much as possible <-
Horse training here is the easiest money you can do while afk.

 

It is impossible to get a Tier 4 horse from 2 lvl 30 Tier 7's. You can get t4 horses from breeding 2 lvl 1 Tier 7's though you must have accidentally bred them before levelling them.