well, I'm not sure who can answer that with any certainty, but if I were to evaluate it, these are my steps to make a decision...
1) Just from looking at the nutritional analysis, it has a lot of Vitamin A (by substantial margin over other vitamins/minerals). It's next closest is vitamin C. So I guess one has to ask what other trace minerals it has that could benefit discus that aren't available elsewhere and how much theny need of it...
2) Next, does the amount of vitamin A fill a deficiency I can't get anywhere else?
3) Do carrots have some physical property that makes me want to add it (binding)
4) The vitamins (trace and otherwise), are they in a digestible form for the discus?
5) Are there alternatives that can provide me with what carrots do and other stuff?
Again, I don't know for sure, but answering those questions are what I would start with.
IMHO, I think I would choose not to add carrots.
... actually, in theory, if I really think about it, I probably should answer those questions with ALL the ingredients I use even if it's popular consensus for some of them. BH has always been debateable, but what about spinach? peas? etc... Not sure I'm qualified to make a proper assessment even if I did do the analysis above.