Precisely.
The foil on the strip is not at all substantial and several Amps current draw will result in significant voltage drop
If nothing else, because the blue LEDs have a higher threshold voltage, when set to full white, the colour will tend to yellow or even orange at a distance from the power injection. This does not of course explain the whole strip going to a uniform colour, but is a limitation of longer lengths of LED strip.
Keep all wiring bundled together - power, ground and control signal. The power "bus" that runs alongside to feed the strip at regular points should preferably not be separate.