The non-specialized stats will decrease while your bloodsmelt higher and higher stats on your esper while specializing in no more than 6. For example, your max attack stat is at 1200, 3 of your resists are at 200, and you are trying to specialize your health stat now. You first make your health stat orange with a best dragon skin, and then you proceed to bloodsmelting it with trigrams then leve75 (cheap Jade Dynasty Gold) divined espers.
As you are bloodsmelting more and more onto your health stat you might notice that every stat except health will have a chance to decrease. This is because your esper is reaching its overall stat maximum. That is why you will see level (Jade Dynasty Gold) 35 espers with 1200 max attack and 20 min attack, and some resistances at 2 points.
You can use the method described in paragraph when your bloodsmelt max attack last because its the stat you desire the most, and an orange stat will never decrease when bloodsmelting. Bloodsmelt that stat last if you value another stat more than attack.
Most people will want an esper with high attack for leveling, regardless of what the other stats are. The process outlined below will cost about 1000 gold and a few hours of your time. Your end result will be an esper with about 700 max attacks if it is leveled to level 30.