First time grower wondering about fox farm...

Hi, i am using a 50 gallon res with fox farm 3 part. I was wondering is stirring something i should do every so often? I noticed that the bottom looks brown like the solution is settling at the bottom. I didnt think this would happen since the solution i thought was water soluable. Also, i was wondering, should i use clearex to flush my ebb and flow table, or is my RO water just fine? I have heard both ways and i was just wondering everyones oppinion. Thank you very much for helping me out with answers...

I would stir it up being the nutes sink. I never used clearex I just use plain water and never had any issue's.