Browser (stock, Chrome, facebook internal browser) crashing topic

Sometimes when I'm browsing ( using Chrome but not necessarily, sometimes when reading an article with Facebook internal browser ) it simply crash without any message, just return to home screen. When I check the used ram is at 450-500-550, signs of an automatically ram clear ( I'm not using any free ram tool ). Seems that the system simply end apps due low ram I suppose but shouldn't start with background apps? Why it clear my foreground application? What do you know about this?

Strangely as it happens lately before I didn't had any similar issues, it doesn't matter how many tabs I had opened in Chrome, never but never crashed. This happens also with the stock Browser so the problem could be the system actually, not an app.

I'm on Stock from sammobile