There shouldn't be an issue mixing them. But, do the jar test if in doubt. Come up with a final NPK value, add them together and toss into a jar, add water, shake and observe. High quality foods will not form precipitates and drop out of solution. I can, and do, take 15 lbs. of plant food, say, a 30-5-15, add to 5 gallons of warm water and it dissolves perfectly and fast with some stirring without precipitates. (In case you're wondering what I'm doing, I'm drip fertilizing thousands of plants.)
The following list is not a complete salts profile, but I'll pull what I don't recommend
based on the NPK values only:
If you need supplements, then the above fails to provide complete nutrition.
Someone pissed off alot of money:
supplements:
general hydroponics kool bloom 2-45-28
supernatural super boost 10-49-10
fox farms big bloom organic 0.01-0.3-0.7
bio grow 1.8-0.1-6.6
humboldts countrys own snow storm 0-0-3
general hydroponics flora nectar 0-0-1
general hydroponics chi 0.2-0-0.2
grandma enngys humic acid
cal mag 2-0-0
botanicare cal-mag
age old grow mycorrhizae
With coco and soil-less mixes, you need 16 essential elements with no one element "outweighing" the other. The only one-for-all product I know of is Dyna-Gro. IOW, for $26 you can have a liter each of a 9-3-6 and a 3-12-6 of a very complete, well designed food which doesn't scam you into buying alot of other crap because the base products are incomplete. Remember, the cannabis industry is all about the money. Profits are OK in my book, scams aimed at noobs who don't know any better are not.
With well prepared potting soils - additional compost, worm castings, peat moss, alfalfa meal and such, you should be using a food designed for such soils like Peters or Schultz. Cheap and it works great. You'll find they have up to 12 essential elements. For example, look at this food's profile:
http://petersabc.com/PDFs/Peters Pro/99720ppro24-8-16FPL.pdf
UB