Lets get back to the topic now
There must be a tiny leak somewhere. I say change the hoses and the radiator cap as well. Buy the genuine radiator cap and don't compromise on quality in this matter.
Get your radiator pressure checked and inspect the coolant/water for head gasket failure. Fill it up, crank the engine, let it idle for couple of minutes and then rev gently to see if there are any bubbles in the water. Also inspect the water for any slime or gunk... a bit brownish yellow in color. If thats the case then it's the ehad gasket.
Hopefully if you do what I said in the beginning, your issue will be resolved. Remember, start with the simplest and cheapest remedies.
Hope your issue gets resolved