Example 3 week steep. 12.915, base, .225FA Custard, .93 maple FA, .93 Marshmallow Capella. Taste has no distinctive note of either flavor. Just muddled sweetness.
EDIT:
Not surprised, all those flavors I normally use as "secondaries", and at lower amounts.
A primary is like Blueberry for example and is usually the highest amount in a recipe.
Say 5% for a primary flavor, (could also be 2 primaries, or 3).
The secondary flavor(s) are usually kept lower, or equal to, the primaries.
(Just a general observation, but there are some exceptions)
(As some primaries are super strong)
(Or if you want to taste more Cream, Milk, Vanilla, etc.,these can become primaries also)
Like: Blueberry Cream vs. Creamy Blueberry
And adding some Maple & Marshmallow to Blueberry works nice.
END EDIT
Other than what's been pointed out:
I'd suggest starting with a 50/50 base, (if you haven't tried this already).
Start with fruits as they are easier to work with than the bakery types IMO.
Even as 1 or 2 flavor mixes.
No EM or sucralose, (Stevia OK in small amounts, i.e. drops).
Like 5% TFA Blueberry Wild, (try 10% next if you can't taste it)
or
3% FA Fuji Apple
or
2-3% INW Strawberry
or
3% Lemon Sicily
(You can add 0.5% FA Marshmallow to those safely, or maybe 0.5-1% TFA Dairy Milk/Sweet Cream)